This may not solve all the problems, but:

First of all, get the new Finale v27 font called “Finale Maestro” which is a SMuFL font based on the Maestro font.

You can e. g. get Finale Maestro by downloading the Finale v27 demo.

Second, there may be some compatibility issues between your Finale v26 and the way a Finale v27 uses special font characters in a SMuFL font.

You could ask the student to send a PDF file of the Finale document, so that you can see the actual layout.

Thanks for the suggestions.  If Finale 26 is not compatible with SMuFL fonts, seems like I'd be out of luck, no?

Old versions of Finale used to have backwards-compatibility save options; I think Finale 2014 offered a "save as 2012" option.  Anyone know if that's an option anymore? 

My students are sending PDFs, but if they have questions about the files themselves, I can't help them.  My school is holding off on upgrades until the whole M1/Big Sur compatibility issues can be definitively resolved.

… If Finale 26 is not compatible with SMuFL fonts, seems like I'd be out of luck, no? …

Perhaps I was not clear enough.

I have been using Finale v26 (and earlier) with SMuFL fonts for years.

Do you have the Finale Maestro font?

To see the font characters you need the SMuFL font.

And do not forget Font Annotation for the font (as with any other new font).

The problem is rather the new Finale v27 documents that use a SMuFL font as Default Music Font.

You may experience display problems if you open a such v27 document in v26, even if you have the SMuFL font.

I don't have Finale Maestro.  I have Maestro.  Where would I get Finale Maestro?

You can e. g. get Finale Maestro by downloading the Finale v27 demo.

You can also have your students send you XML files (just XML 3, not XML 4) or Finale 2012 files.

My school is holding off on upgrades until the whole M1/Big Sur compatibility issues can be definitively resolved.

There are no Big Sur issues with Finale 26 or Finale 27. 
https://www.finalemusic.com/blog/finale-v26-compatibility-with-macos-big-sur/

And while MM states "we do not recommend using Finale with M1 computers and do not consider these within our current system requirements", they also state that "Apple's Rosetta 2 is showing promising results and we have seen no major issues, but more testing needs to be done." 

 Perhaps it might be useful to ask MM for an update on all the testing they been doing since the debut of M1 hardware in November 2020. Anecdotally, Finale seems to run fine under emulation. 

"If Finale 26 is not compatible with SMuFL fonts, seems like I'd be out of luck, no?"

I would not d/l the smufl fonts.  But MM used to have the Fontpack (one word) for d/l. It has all the regular, normal, fonts in it.

Go to the MM site and click on downloads.