Did you by chance have a custom comskip.ini file on your Mint install that didn’t get migrated to your Mac? For me customizing my comskip.ini made a big difference in commercial detection over the default.
If you had it on your Plex Mint install it would have been at /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/DVR/comskip.ini. This is a good support article for where to find this on different OSes (under " Customizing How Commercials are Located and Removed".) I haven’t modified my comskip.ini for several years, but I think I based mine on the @JasonNalley post here.
