Yes, this steps also work under Lineage 18.1.Just to partially answer my question:
Using Magisk can solve this issues.
How can I safely install Magisk?
I found some instructions like:
1) Download magisk.apk
2) rename it to magisk.zip
3) sideload this .zip file from TWRP
4) install magisk.apk
Do these steps also work under Lineage 18.1?
After installing magisk install you also need to install safetynet-fix-v2.3.1-MOD_2.0
Then disable wifi (and mobile data) and delete data of play service and playstore. Reboot your device, enable internet access again and your device should be verified.