Pulled the Trigger ...

... on upgrading to the new 64-bit Raspberry Pi OS.

Instead of ordering and waiting for a 256 Gb micro SD card, I used a 64Gb USB drive. After various problems with things like:

1.  Making it bootable (e.g. contra several tutorials, I was NOT able to just set a boot order so it's one or the other -- if the SD card is in there, that's what it boots from);
2. Getting my preferred text editor, Caret, to work (when I installed it as a Vivaldi app, it couldn't load or save files; I installed it as a Chromium app, problem solved);

And so on and so forth, I've now got essentially the same setup I had before, but it anecdotally feels like it runs faster, and now I can install 64-bit apps.

By "same setup I had before," I include at least one existing problem, which is not being able to get Widevine to work so that I can watch DRM content in Vivaldi. But that hasn't been a big deal anyway. When I want to watch TV, I do it ON the TV ... and if I REALLY don't feel like that, well, my old Amazon Fire TV stick is plugged into the extra HDMI port on one of my monitors, so I can just switch inputs and run a movie on the left screen while I work on the right screen. I think I've done that a grand total of one time ever, though.