@keneda I assumed Lineage 15.1 would suffice for Android 8, so was able to flash with that. Re-ran install with installer version 0.9.7 (Snap on Ubuntu box). It recognized the device and did install then at end, got the "ADB is Scanning for Devices" - walked away a few mins and it now is just in a bootloop, flashing this message "E:failed to mount /cache (Invalid argument), E:Can't mount /cache/recovery/last_locale". Any ideas on why, or what to do to solve this? Thanks!

@keneda Thanks much! I'm a beginner, have just flashed phones with pre-built ROMs.

Unsure about Android 8 (A8), because there's no "stock" A8 for Karin, I understood https://forum.xda-developers.com/t/no-android-8-oreo-for-our-z4-tablets.3679395/.

Also, installer page implied Halium 7.1 needed Android 7.1 (already there) to match the Halium version. ¹ Devices generally require a specific version of Android/stock rom to be installed. This depends on the halium version the port is build on. For example, if the port is based on halium 9, make sure you have Android version 9 installed before running the installer.

How do I build stock Android 8 for this device?

I too have the Karin device and experienced the exact same err using the installer as @z4Tab--> e:failed to mount /cache (Invalid argument) etc.. Right now, device has nothing but TWRP on it and I can't seem to get any UBTouch installed. I started the install with stock Android 7.1 installed. Got some message that I may need Android 8 installed but ignored that. Saw lots of files in @Guf post, but don't know how to use them. Is there a step-by-step install doc that explains how? I tried to flash system5.img and got a TWRP err like "Size of image is larger than target device." So, I'm not sure how to proceed, any help is appreciated.