@Keneda Wow, thanks for the great answer. This is really messy. I am pretty shocked how bad everything gets once you leave the area of Opensource. 
Nevertheless, I will try to contact these guys, they reflash Volla Firmware on Volla.
They should have what is needed to restore a rephone with Volla OS, although it's not listed on their services page. But maybe, just maybe I can convince them.
https://phone-service.de/r/volla/#
Source: https://github.com/ubports/ubports-installer/issues/3450
Some output from mtkclient
Port - Device detected :)
Preloader - CPU: MT6768/MT6769(Helio P65/G85 k68v1)
Preloader - HW version: 0x0
Preloader - WDT: 0x10007000
Preloader - Uart: 0x11002000
Preloader - Brom payload addr: 0x100a00
Preloader - DA payload addr: 0x201000
Preloader - CQ_DMA addr: 0x10212000
Preloader - Var1: 0x25
Preloader - Disabling Watchdog...
Preloader - HW code: 0x707
Preloader - Target config: 0xe0
Preloader - SBC enabled: False
Preloader - SLA enabled: False
Preloader - DAA enabled: False
Preloader - SWJTAG enabled: False
Preloader - EPP_PARAM at 0x600 after EMMC_BOOT/SDMMC_BOOT: False
Preloader - Root cert required: False
Preloader - Mem read auth: True
Preloader - Mem write auth: True
Preloader - Cmd 0xC8 blocked: True
Preloader - Get Target info
Preloader - BROM mode detected.
Preloader - HW subcode: 0x8a00
Preloader - HW Ver: 0xca00
Preloader - SW Ver: 0x0
Preloader - ME_ID: 1B48AD47B284C534F53316D6C5F3AC62
Preloader - SOC_ID: C3002168C34FCB653FC9F08789B4714DA6D5BD43713DD0A6E25D5E5CC28D126D
DA_handler - Device is unprotected.
DA_handler - Device is in BROM-Mode. Bypassing security.
PLTools - Loading payload from mt6768_payload.bin, 0x264 bytes
PLTools - Kamakiri / DA Run
Kamakiri - Trying kamakiri2..
Kamakiri - Done sending payload...
PLTools - Successfully sent payload: /usr/lib/python3.11/site-packages/mtkclient/payloads/mt6768_payload.bin
Port - Device detected :)
DA_handler
DA_handler - [LIB]: Device is in BROM mode. No preloader given, trying to dump preloader from ram.
Successfully extracted preloader for this device to: preloader_k69v1_64_k419.bin
DAXFlash - Uploading xflash stage 1 from MTK_AllInOne_DA_5.2228.bin
xflashext - Patching da1 ...
Mtk - Patched "Patched loader msg" in preloader
Mtk - Patched "hash_check" in preloader
xflashext
xflashext - [LIB]: Error on patching da1 version check...
Mtk - Patched "Patched loader msg" in preloader
Mtk - Patched "get_vfy_policy" in preloader
xflashext - Patching da2 ...
DAXFlash - Successfully uploaded stage 1, jumping ..
Preloader - Jumping to 0x200000
Preloader - Jumping to 0x200000: ok.
DAXFlash - Successfully received DA sync
DAXFlash - Sending emi data ...
DAXFlash - DRAM setup passed.
DAXFlash - Sending emi data succeeded.
DAXFlash - Uploading stage 2...
DAXFlash - Upload data was accepted. Jumping to stage 2...
DAXFlash - Successfully uploaded stage 2
DAXFlash - EMMC FWVer: 0x0
DAXFlash - EMMC ID: 3V6CAB
DAXFlash - EMMC CID: 15010033563643414202e81a6ab69871
DAXFlash - EMMC Boot1 Size: 0x400000
DAXFlash - EMMC Boot2 Size: 0x400000
DAXFlash - EMMC GP1 Size: 0x0
DAXFlash - EMMC GP2 Size: 0x0
DAXFlash - EMMC GP3 Size: 0x0
DAXFlash - EMMC GP4 Size: 0x0
DAXFlash - EMMC RPMB Size: 0x1000000
DAXFlash - EMMC USER Size: 0x1d1ec00000
DAXFlash - HW-CODE : 0x707
DAXFlash - HWSUB-CODE : 0x8A00
DAXFlash - HW-VERSION : 0xCA00
DAXFlash - SW-VERSION : 0x0
DAXFlash - CHIP-EVOLUTION : 0x1
DAXFlash - DA-VERSION : 1.0
DAXFlash - Extensions were accepted. Jumping to extensions...
DAXFlash - DA Extensions successfully added
GPT Table:
-------------
proinfo: Offset 0x0000000000008000, Length 0x0000000000300000, Flags 0x00000000, UUID f57ad330-39c2-4488-b09b-00cb43c9ccd4, Type EFI_BASIC_DATA
misc: Offset 0x0000000000308000, Length 0x0000000000080000, Flags 0x00000000, UUID fe686d97-3544-4a41-21be-167e25b61b6f, Type EFI_BASIC_DATA
para: Offset 0x0000000000388000, Length 0x0000000000080000, Flags 0x00000000, UUID 1cb143a8-b1a8-4b57-51b2-945c5119e8fe, Type EFI_BASIC_DATA
expdb: Offset 0x0000000000408000, Length 0x0000000001400000, Flags 0x00000000, UUID 3b9e343b-cdc8-4d7f-a69f-b6812e50ab62, Type EFI_BASIC_DATA
frp: Offset 0x0000000001808000, Length 0x0000000000100000, Flags 0x00000000, UUID 5f6a2c79-6617-4b85-02ac-c2975a14d2d7, Type EFI_BASIC_DATA
vbmeta_a: Offset 0x0000000001908000, Length 0x0000000000800000, Flags 0x00000000, UUID 4ae2050b-5db5-4ff7-d3aa-5730534be63d, Type EFI_BASIC_DATA
vbmeta_system_a: Offset 0x0000000002108000, Length 0x0000000000800000, Flags 0x00000000, UUID 1f9b0939-e16b-4bc9-bca5-dc2ee969d801, Type EFI_BASIC_DATA
vbmeta_vendor_a: Offset 0x0000000002908000, Length 0x0000000000800000, Flags 0x00000000, UUID d722c721-0dee-4cb8-838a-2c63cd1393c7, Type EFI_BASIC_DATA
vbmeta_b: Offset 0x0000000003108000, Length 0x0000000000800000, Flags 0x00000000, UUID e02179a8-ceb5-48a9-3188-4f1c9c5a8695, Type EFI_BASIC_DATA
vbmeta_system_b: Offset 0x0000000003908000, Length 0x0000000000800000, Flags 0x00000000, UUID 84b09a81-fad2-41ac-0e89-407c24975e74, Type EFI_BASIC_DATA
vbmeta_vendor_b: Offset 0x0000000004108000, Length 0x0000000000800000, Flags 0x00000000, UUID e8f0a5ef-8d1b-42ea-2a9c-835cd77de363, Type EFI_BASIC_DATA
md_udc: Offset 0x0000000004908000, Length 0x000000000169a000, Flags 0x00000000, UUID d5f0e175-a6e1-4db7-c094-f82ad032950b, Type EFI_BASIC_DATA
metadata: Offset 0x0000000005fa2000, Length 0x0000000002000000, Flags 0x00000000, UUID 1d9056e1-e139-4fca-0b8c-b75fd74d81c6, Type EFI_BASIC_DATA
nvcfg: Offset 0x0000000007fa2000, Length 0x0000000002000000, Flags 0x00000000, UUID 7792210b-b6a8-45d5-91ad-3361ed14c608, Type EFI_BASIC_DATA
nvdata: Offset 0x0000000009fa2000, Length 0x0000000004000000, Flags 0x00000000, UUID 138a6db9-1032-451d-e991-0fa38ff94fbb, Type EFI_BASIC_DATA
persist: Offset 0x000000000dfa2000, Length 0x0000000003000000, Flags 0x00000000, UUID 756d934c-50e3-4c91-46af-02d824169ca7, Type EFI_BASIC_DATA
protect1: Offset 0x0000000010fa2000, Length 0x0000000000800000, Flags 0x00000000, UUID a3f3c267-5521-42dd-24a7-3bdec20c7c6f, Type EFI_BASIC_DATA
protect2: Offset 0x00000000117a2000, Length 0x000000000085e000, Flags 0x00000000, UUID 8c68cd2a-ccc9-4c5d-578b-34ae9b2dd481, Type EFI_BASIC_DATA
seccfg: Offset 0x0000000012000000, Length 0x0000000000800000, Flags 0x00000000, UUID 6a5cebf8-54a7-4b89-1d8d-c5eb140b095b, Type EFI_BASIC_DATA
md1img_a: Offset 0x0000000012800000, Length 0x0000000008000000, Flags 0x00000000, UUID a0d65bf8-e8de-4107-3494-1d318c843d37, Type EFI_BASIC_DATA
spmfw_a: Offset 0x000000001a800000, Length 0x0000000000100000, Flags 0x00000000, UUID 46f0c0bb-f227-4eb6-2fb8-66408e13e36d, Type EFI_BASIC_DATA
scp_a: Offset 0x000000001a900000, Length 0x0000000000600000, Flags 0x00000000, UUID fbc2c131-6392-4217-1eb5-548a6edb03d0, Type EFI_BASIC_DATA
sspm_a: Offset 0x000000001af00000, Length 0x0000000000100000, Flags 0x00000000, UUID e195a981-e285-4734-2580-ec323e9589d9, Type EFI_BASIC_DATA
gz_a: Offset 0x000000001b000000, Length 0x0000000001000000, Flags 0x00000000, UUID e29052f8-5d3a-4e97-b5ad-5f312ce6610a, Type EFI_BASIC_DATA
lk_a: Offset 0x000000001c000000, Length 0x0000000000200000, Flags 0x00000000, UUID 9c3cabd7-a35d-4b45-578c-b80775426b35, Type EFI_BASIC_DATA
boot_a: Offset 0x000000001c200000, Length 0x0000000002000000, Flags 0x00000000, UUID e7099731-95a6-45a6-e5a1-1b6aba032cf1, Type EFI_BASIC_DATA
vendor_boot_a: Offset 0x000000001e200000, Length 0x0000000004000000, Flags 0x00000000, UUID 8273e1ab-846f-4468-99b9-ee2ea8e50a16, Type EFI_BASIC_DATA
dtbo_a: Offset 0x0000000022200000, Length 0x0000000000800000, Flags 0x00000000, UUID d26472f1-9ebc-421d-14ba-311296457c90, Type EFI_BASIC_DATA
tee_a: Offset 0x0000000022a00000, Length 0x0000000000600000, Flags 0x00000000, UUID b72ccbe9-2055-46f4-67a1-4a069c201738, Type EFI_BASIC_DATA
sec1: Offset 0x0000000023000000, Length 0x0000000000200000, Flags 0x00000000, UUID 9c1520f3-c2c5-4b89-4282-fe4c61208a9e, Type EFI_BASIC_DATA
boot_para: Offset 0x0000000023200000, Length 0x0000000001a00000, Flags 0x00000000, UUID 902d5f3f-434a-4de7-8889-321e88c9b8aa, Type EFI_BASIC_DATA
nvram: Offset 0x0000000024c00000, Length 0x0000000004000000, Flags 0x00000000, UUID bece74c8-d8e2-4863-fe9b-5b0b66bb920f, Type EFI_BASIC_DATA
logo: Offset 0x0000000028c00000, Length 0x0000000000c00000, Flags 0x00000000, UUID ff1342cf-b7be-44d5-5ea2-a435addd2702, Type EFI_BASIC_DATA
md1img_b: Offset 0x0000000029800000, Length 0x0000000008000000, Flags 0x00000000, UUID a4da8f1b-fe07-433b-cb95-84a5f23e477b, Type EFI_BASIC_DATA
spmfw_b: Offset 0x0000000031800000, Length 0x0000000000100000, Flags 0x00000000, UUID c2635e15-61aa-454e-409c-ebe1bdf19b9b, Type EFI_BASIC_DATA
scp_b: Offset 0x0000000031900000, Length 0x0000000000600000, Flags 0x00000000, UUID 4d2d1290-36a3-4f5d-b4af-319f8ab6dcd8, Type EFI_BASIC_DATA
sspm_b: Offset 0x0000000031f00000, Length 0x0000000000100000, Flags 0x00000000, UUID fdce12f0-a7eb-40f7-5083-960972e6cb57, Type EFI_BASIC_DATA
gz_b: Offset 0x0000000032000000, Length 0x0000000001000000, Flags 0x00000000, UUID 0fbbafa2-4aa9-4490-8389-5329328505fd, Type EFI_BASIC_DATA
lk_b: Offset 0x0000000033000000, Length 0x0000000000200000, Flags 0x00000000, UUID a76e4b2f-31cb-40ba-6a82-c0cb0b73c856, Type EFI_BASIC_DATA
boot_b: Offset 0x0000000033200000, Length 0x0000000002000000, Flags 0x00000000, UUID f54ac030-7004-4d02-8194-bbf982036807, Type EFI_BASIC_DATA
vendor_boot_b: Offset 0x0000000035200000, Length 0x0000000004000000, Flags 0x00000000, UUID c4c310e2-4a7e-77d3-1848-61e2d8bb5e86, Type EFI_BASIC_DATA
dtbo_b: Offset 0x0000000039200000, Length 0x0000000000800000, Flags 0x00000000, UUID 3734710f-0f13-1ab9-4c73-12a08ec50837, Type EFI_BASIC_DATA
tee_b: Offset 0x0000000039a00000, Length 0x0000000000600000, Flags 0x00000000, UUID 85a5b02f-3773-18b3-4910-718cde95107e, Type EFI_BASIC_DATA
super: Offset 0x000000003a000000, Length 0x0000000200000000, Flags 0x00000000, UUID 6fce83a6-5273-4748-4511-c205ebb4b8ad, Type EFI_BASIC_DATA
userdata: Offset 0x000000023a000000, Length 0x0000001ae10f8000, Flags 0x00000000, UUID 3645e6a3-a7e3-19b2-4149-172c10190eef, Type EFI_BASIC_DATA
otp: Offset 0x0000001d1b0f8000, Length 0x0000000002b00000, Flags 0x00000000, UUID f60b92b4-0e2f-91b6-4afb-2d0b643bab4b, Type EFI_BASIC_DATA
flashinfo: Offset 0x0000001d1dbf8000, Length 0x0000000001000000, Flags 0x00000000, UUID d05cedfe-20b7-68b3-f259-4fe25317f2fc, Type EFI_BASIC_DATA
Total disk size:0x0000001d1ec00000, sectors:0x000000000e8f6000
@flinke-vent I am having the exact same issue. I used ubport-installer 0.10.0 on a Rephone and all I get is a white charging LED. No vibrations on longpresses, no fastboot, no nothing. Where did I mess up? I tried it with Volla22 wich should work on Rephone accoring to this: https://forum.sailfishos.org/t/volla-installation-guide/16658