While using the newer versions of the software found some bugs or lost features.
Small font because I could fix that installing the version for older macOS version even if I am using a newer version of that OS (but with a patcher).
Version 2.4.1. Sadly it wouldn't open. If that matters, I have Qjackctl installed and running and tried openiung Polyphone, for discarting things.
Termination Reason: Namespace DYLD, Code 1 Library missing Library not loaded: /System/Library/Frameworks/Jackmp.framework/Versions/A/Jackmp Referenced from: <888AAD44-93F2-37A9-8619-39E6B0E96572> /Applications/Polyphone 2.4.1.app/Contents/MacOS/polyphone Reason: tried: '/System/Library/Frameworks/Jackmp.framework/Versions/A/Jackmp' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/System/Library/Frameworks/Jackmp.framework/Versions/A/Jackmp' (no such file), '/System/Library/Frameworks/Jackmp.framework/Versions/A/Jackmp' (no such file, not in dyld cache), '/Library/Frameworks/Jackmp.framework/Versions/A/Jackmp' (no such file) (terminated at launch; ignore backtrace)"
Having the version 2.4.1 running, found that key ranges cannot be assigned as in older versions, in which I could press in a MIDI keyboard two notes and then having the values change to that. Polyphone now only recognizes the first note and not the second.