Thank you for this.The OP has a guide on how to remove modules using ADB.
This is it:
1. Connect your phone to your computer.
2. Reboot the phone, then during the boot animation enter this command via ADB.
adb wait-for-device shell magisk --remove-modules
3. Allow to boot, modules will be removed and root should then be active.
Otherwise a safe mode boot will disable Magisk from being used until next boot.
Also don't flash the boot image, just boot it.
fastboot boot (name of image)
Also make sure you are patching it with stable Magisk not beta nor Canary..
If it fails to boot up after the fastboot command then obtain another boot image and re-patch it.
Should be fine then.
PS: ideally you want to stick with full updates (if available) not OTA's, I'd recommend oxygen updater for that reason.
This worked and I'm rooted again.
Also, I misunderstood the terminology, byt OTA I did mean using Oxygen Updater.
Thank you again