I was able to flash the older (v18.1) magisk patched boot image using fastboot. I will attach the image here if you need too. I had to split the RAR file into 3 parts due to limitation of XDA of RAR files to be 8MB.
Root is working fine, I was able to grant access to Titanium Backup. But seriously that was messed up. If that happened to my Shield TV and I lost all of my games I will be furious. Luckily, I tried that on the Shield TV before knowing it will mess up my Xperia 10 plus phone. What is more messed up is there is no way from Magisk Manager to keep using older APK or download older version of Magisk, I tried Custom URL in the settings to check the update from, but all I got was a spinning wheel while checking for updates.
Currently running Magisk Manager 7.1.2 and v18.1 , just ignoring the ZIP update.
Rule of thumb, if it aint broken, don't fix / update.