reply to myself, this is already answered here
Since I also had problems with the restrictive memory policy on A11, I downgraded to Berni's LiOS 17.1. Unfortunately, after booting, the phone always hung and rebooted shortly after. I already wanted to give up and took out the external SD card in preparation for flashing the Stock Rom again, but then the system was suddenly stable. After having changed the partition of the external SD card from exFAT to FAT32, everything now runs stable and smoothly.
dirty flashing over 17.1 is working. (I've never tried it before though.)
After flashing the 18.1 ROM, remember to reflash magisk before rebooting, in order to preserve Magisk environment.
For signature spoofing, just follow what you did on your previous device, so that microG could work.
How do this version LineageOS 18.1 and the previous version (LineageOS 17.1) compare with respect to performance, battery drain, memory usage ... any opinions on this?
I've read the whole thread and collected some relevant quotes below. They're somewhat conflicting.
adb root adb shell logcat -b all -d > logcat
adb pull /sys/fs/selinux/policy
cd sys/fs/pstore cp * /sdcard