so after I've read your piece of wisdom about installing all on same drive, I decided to uninstall BIAB 2021 and to install it on the same external drive where I'll install, anew, the upgrade. Good idea, right? No it isn't: DIAB (Devil in a Box) now says that the realtracks pro 2. or whatever they are called, can ONLY be installed on the drive where MacOs is running. That's why realtrack pro 1 was stuck, in true DIAB fashion, so I had to force quit.

With the result that this was all a big waste of time, since I am none the wiser. Fortunately I have a backup on another external SSD drive, so I can just plug in and have the old DIAB working, at least, along with all else.

''Deep and rich'', uh?