Catalina 10.15.7 and Security Update 2021-002 with minimal SIP settings breaks TotalSpaces2 and stops Mac from booting

I’ve been using TotalSpace2 v2.9.8 for a while now on Catalina on a Mac Pro 2019 with FileVault enabled.
All has been good until I applied the April 2021 Catalina Security Update last night.

Applying the security update resulted in my Mac failing to boot correctly - I’d get the miniroot boot loader, it would accept my password and then go into a black screen with the apple logo and a progress bar, which would get to about 60% before going into the white circle ‘prohibitory symbol’ and stopping, which required a power cycle.

After trying to reboot about 6 times, I eventually did a PRAM reset and the Mac finally booted BUT TotalSpaces2 was not able to run and I had to work like this for a day as I couldn’t afford any more downtime to debug.

This evening I booted into recovery mode and ran the following to minimally disable certain parts of SIP.

csrutil enable --without debug --without fs

This was accepted, I rebooted and I was back to the same problem of the Mac failing to boot until yet another PRAM reset.

I then decided to completely disable SIP from recovery mode:

csrutil disable

After rebooting this time, the Mac did finally boot and I was able to launch TotalSpaces2 successfully.

I have no idea if the Security update screws with the ‘fs’ part of SIP or if FileVault has it’s part to play here but after spending a day with the default grid manager, I was ready to tear my hair out so I’m glad that I could get TotalSpaces2 back.