I followed Lineage OS wiki:
But instead installing LineageOS recovery I installed TWRP:
I managed to boot TWRP at first, but had problems later, for some reason device started stock recovery when power + volume up, got forward from there I had to follow guide how to reboot phone to twrp recovery from PC cmd / terminal (I use linux).
Double check these if you have similar issues, but I think it was something like, connect phone to PC (at this point I had bootloader opened and USB setted back to debug mode). If you don’t have this problem skip this booting to twrp recovery part. This is written partially from memory, so that’s why search and verify somewhere if you try following. I will doulple check later, but at quickly glance it seems right to me. Can’t find now what guide I was using selectively.
sudo adb devices (if on windows, no sudo)
(check if PC finds phone)
sudo adb bootloader
sudo fastboot devices
(check if fastboot finds phone)
sudo fastboot reboot recovery
I don’t actually recall for sure did phone booted directlt to twrp after that or did I need to hold power + power up.
After this I made backup from my stock rom following this guide:
Note: I didn’t copy data cause in my case it was empty and while trying keeping it on causede error at the end.
Now when backup is ready I connected phone to PC and copied backup files to PC just in case. After that I jumped back to following Lineage OS Wikipage. Just note that wikipage is using LineageOS Recovery iin the guide, twrp is bit different but needed functionality for sideload can be found there also.
After I flashed /e/ OS image at the step where wikipage sideloads LineageOS image, I also sideloaded Magisk cause I knew I was going to need that for testing porposes, but it’s not neccesary needed.
If everything goes fine things are quite straightforward after this, just starting and setting phone up with /e/ account.
Note: This was my first time I used sideload option and only second time to install custom rom in general, so that’s the reason I don’t remember all exact steps I faced, but in generally things should be able to done at this way and Lineage OS wiki is good friend to start. Also don’t do something if you are not sure of.
Edit: Could you @itsclarence correct me if I made some mistakes above, you have more experience. Especially mistakes which could lead to bricked device should always be ironed out, that’s why I also sis it’s better double check. On the other hand bricked device is always one possible scenario what could happem if things go wrong.