The official Lineage recovery should be able to do this as well. Wipe system and cache in the "factory reset" menu, then re-install ROM and GApps with adb sideload.You can try to manually update the ROM / fix bootloop.
- Download the ROM+GApps in your PC
- Boot to twrp by REIGNZ based on A12 System_Ext
- Transfer the ROM+Gapps while u are connected to pc and in twrp
- Wipe System, System_ext, Vendor, Dalvik Cache, Cache
- Flash the updated build, Gapps
- Boot to system
- If it works boot to twrp again and flash Magisk.
The "magisk binaries" error is unavoidable if you don't use a recovery that can decrypt data tho. It means that Magisk was not kept after the update. You need to manually re-install Magisk with the boot image patch method. An alternative is "Lygisk". It moves the "Magisk binaries" to an unencrypted space, but only if the encryption method is FBE, not FDE, if I recall correctly.