Logic completely crashing MacBook

Yes please provide Etrecheck report.

"....I really need to write some music right now :( updating your system shouldn’t leave it completely unusable....."

I would urge anyone who uses any computer for work or a serious hobby to take the following action before committing to an OS upgrade .

You were given the choice of upgrading or not.

You were strongly recommended to take backups.

You had the opportunity to research this forum and also the wider web to see what possible problems your mac might experience.

You could have taken a non-work day to test out Catalina and your key apps, and within  hours work out if it was for you or not. i.e. keep or revert.

Apple make it easy for you to revert to the original OS, even publishing simple instructions and a free Time Machine program, the best backup app on the market.

FWIW, XQuartz appears to work here. I have from way back when, and just launched in Catalina as a test. I no longer have any relevant applications that rely on XQuartz, but at least the terminal and man work ok.

About 90GB is “available” but only 15GB appears as “free”. It ought to work but apparently the purgeable space is not always recovered in a timely manner.

Try restarting in Safe Mode and then restarting normally again.

You talk about making music but this Mac looks more like a gaming machine. Am I right?

There are several things I would recommend in no particular order.

The obvious one is the crash involving Bittorrent and dungeon. Check you have the latest versions or get rid if no longer used.

Your Mac needs a good. clear out. Get Free app Go64 as a start and get rid of the many 32 bit apps.

Clear out all your login items and plugins. They may even involve 32b it apps

All your remaining 64bit apps then need to be checked for updates from the site they came from.

Delete any you no longer use.

You have steamcleaner installed to presumably clear out GB's of gaming detritus - have you tried using it to do the clear out?

The Time Machine is the same size as the Mac disk - it should be at least twice the size ie 1TB or more

If you really want that old technology (xquartz and bittorrent seem rather old now) then revert to Mojave.

Forgot to day you are two updates behind 10.15.3 The .3 has fixed many crashes.

Please run Etrecheck and post its report here.

You need to clear some space from your drive NOW.

How much space do you have now? What you had before was bound to cause slowness and crashes.

Can you run Etrecheck now and post the new report?

Give it full disk access this time

btw Are you sure xquartz is still supported. Thought it was dropped with Sierra.

Those in the report plus any others you know about.

Start with the ones you know you don't need.

Then the ones you do need.

Elimination and iteration.