I work from home (since about a month...), I could theoretically use my old 2012 Mini - but that would defeat the purpose. And I'd need a new display (which was the larger reason to buy the 2018 to begin with...)
Since it happened after a security or software update, you're entitled to phone support. Take advantage of it. Yes, they'll make you jump through hoops but you can limit the time and schedule follow-up. I also work from home (since 2007) so I have to schedule this, too.
If you have AppleCare as I do, it might push the priority higher, don't really know.
My suspicion is that there is not one "fix". Given all the things that the T2 does it is likely that we are seeing a lot of different problems.
Well, they are working on a patch for an upcoming beta of Catalina 10.15.5. If I were to guess, it would be after that was thoroughly tested, then they'd work on another security update for Mojave—but we need them to get off the stick now.
I could do a lot of my work on my 2012 MBP (yikes!) but not everything.
As I never let the CPU sleep, only the display, it's manageable for me. That's no reason to let up on the pressure.
Unfortunately, though I live only 2 miles away from the Mother Ship in Cupertino, current lock down conditions prevent me from taking my machine in and letting Apple have at it.