I used to have good luck using pdftk for filling out forms and the IRS seemed to encode them well, but it looks like pdftk is mostly dead. Nowadays, evince seems to work OK, sometimes, for filling out forms. And, yes, Acrobat seems to be the only piece of software that does all of them.

That said, my personal favorite for a complete screw you to the format comes from Texas and form 2382:

https://hhs.texas.gov/laws-regulations/forms/2000-2999/form-...

If you decompress it, you'll find that they encoded an HTML webpage into the PDF and, as far as I can tell, this can only be viewed on Windows with Acrobat. It's almost like Texas doesn't want people to apply for medicaid funds.