Catalina, no problem with Finale 26.3.1, according to MakeMusic.

Now, a brand new Mac may come with MacOs 11 (Big Sur). It should be ok, unless you buy a Mac with the M1 processor, not recommended (yet) by MakeMusic.

Dear Michel:

Thanks a lot. That's a big help.  I heard about that new processor. I will have to watch that.

The M1 (Apple Silicon) Macs cannot run on Catalina. The latest Intel Macs can — even if they don't ship with it. Various ways to make that happen but no need to cross that bridge before it's an issue.

As for Finale over Big Sur:

"After thorough testing on macOS 11 Big Sur, we have determined that Finale v26.3.1 is compatible with this OS. We are not aware of any major issues that prevent the program from operating as expected. There are, however, a few minor cosmetic issues that are present and we will continue to work with Apple to address these. For more information on these, visit the articles linked below."

Back to the M1. These come with Rosetta 2, an Intel Mac emulator but still Big Sur. Once MM has declared Finale compatible with Rosetta 2, the M1 will no longer be an issue while we wait for full AS compatibility. Till then, the official word it still

"While Apple’s Rosetta 2 is showing promising results, more testing needs to be done."  

In the mean time, check back here often for the latest news:

https://www.finalemusic.com/blog/finale-v26-compatibility-with-macos-big-sur/