Well, @doniks, I have tried creating files of various sizes with dd and doing an adb push with them, and there are some results: -Images of 1 GB or 1,5 GB are not created by an error of insufficient space in halium-install -Images of 2 GB or more are created but when I try to push it to the phone vía adb push (filename) /data it gives me an error of not enough partition size. I have tried it not only with Ubuntu Touch images, also with Plasma Mobile rootfs and Halium reference rootfs.

@synnyg_r If you flashed via script halium-install-standalone.sh dont forget to add argument with -p ut halium-install-standalone.sh -p ut path/to/rootfs.tar.gz path/to/system.img

https://pastebin.com/EUgabSTY Its going in the right direction... 2 days later and I'm stuck on a grafik error / memory setup error [ 127.543935] subsys-pil-tz soc:qcom,kgsl-hyp: a530_zap: loading from 0x000000008fe00000 to 0x000000008fe02000 [ 127.561301] subsys-pil-tz soc:qcom,kgsl-hyp: a530_zap: Memory setup error

@JCLemme Ok but then smth is really broken, I would suggest to start building a LineageOS tree from scratch, and get their recovery working. Or, use TWRP as recovery, try to boot boot.img from your build, let it crash and then go into TWRP, use adb and get /proc/last_kmsg if possible