I ended up buying a new Mac Mini desktop so I could upgrade the OS to the current Tahoe version, but then I saw I still had to pay for Diarium again, for the desktop version for another $16 after tax, but still saw no way to import the years of MacJournal entries, so I exported them to text files that I could copy from, and paste into Diarium, but of course, that’s going to be a long process for 30 years worth of entries.
Now I see that Apple’s Journal app is available on my tablet. I had not used it when it was an iPhone-only app, but if they make it for use on iPad and desktop I may start using that, since I will have to copy and paste anyway in either app (I see NO import option for Journal) but I also hate to have spent over $26 on Diarium, just to switch over to Journal now…