Microsoft converts Office 2019 for Mac perpetual licenses to read-only versions
(consumerrights.wiki)
When I sold customers office a couple years ago. I would give them two options, you can go with MS365( or what ever bullshit they call it now) and pay the yearly subscription to always have the newest product. Or you could buy perpetuals and hope they don't start sunsetting perpetuals faster than they did back then. They have always made perpetuals unusable after 6+ years through one mechanism or another.