I'm still on Mojave to use 32-bit apps. Any way to use 32-bit in Catalina or later?
You can sometimes get away with copying a handful of individual frameworks from older versions of macOS to newer ones, (I recently got Mountain Lion's QuickTime to work on Mavericks this way), but for so many libraries, many of which operate at a low level, it's just not going to happen!
Mojave is still a perfectly fine OS for a while longer. And you can of course use virtual machines, although personally I'd probably opt for dual booting if it really came to that.
I did try this, when Catalina first came out. But maybe I gave up too quickly (It was a "there is no way this will actually work" type of thing), or maybe I tried the wrong app...
It's possible to get a Mojave VM up and running but it was nontrivial when I gave it a shot