FCPX downgrade - updated libraries won't open - workaround?

Hi - I am about to downgrade from Big Sur to Catalina (Big Sur was crashing my Macbook for months - no solution). So I have assume I will be forced to downgrade my FCPX as well. Naturally I'd like to open my Libraries but they will no longer be openable. So what is the workaround to be able to work on Catalina with a lower version of FCP and "updated" libraries?

Will I lose all my Libraries?

Is a workaround possible? such as I export timelines as XML and then, downgrade FCP and import the XMLs again and try and link with media?

I doubt I'll go to Big Sur again - too much unreliability for no benefit. So I am stuck on Catalina and an older FCP. I can't be the only one to downgrade and be stuck like this?