There are a couple of things that seem to work. The beatsaber work around seems to work as well without using the temporary legacy version via "JustInCaseWeNeedIt"
1/ Find appmanifest_221860.acf in steamapps folder
2/ open with Notepad
3/ Change the number after "stateflags" from "6" to "4" (6 means update - 4 means already updated)
4/ Change the number 4556485830000690187 to 8947385950072815198
5/ Save file and restart steam
Possible 6/ Set the appmanifest file to read only
I did this BEFORE the update happened so not sure about after it's been done
But we're still stuck with the updated version if you can't get to it in time or if you ever format your hard drive or get a new PC.