Thank you to everyone for your suggestions! I’m still plugging away at Linux, and mostly adapting just fine. My major complaints right now are with my reflexes: cut/copy/paste are handled with the control key in Linux, while in Mac OS X you have to hold down the command key, which means that every time I intend to copy some text, I instead delete it and replace it with the letter “c”, followed by a panicky attempt to undo it by adding a “z”. Also, Pop!_OS uses the command key by itself to switch to a system menu and a display of running apps, so it’s like the screen explodes in confusion every time I make an elementary mistake. Lesson learned: stop making mistakes. Or get my pinky trained to press the correct modifier button.
I’m also experiencing the joy of non-Mac klunkiness. I tinkered with KDENLive as a replacement for iMovie. It’s got some things iMovie lacks, like as many track layers as you want. On the other hand, iMovie is easy — you click on an object in a layer, tell the program to apply the green screen effect, and everything green turns transparent. In KDENLive, you do the same thing, and in addition to requiring that you set a bunch of parameters to define what “green” is, it turns everything else transparent. I’m going to have to go through a bunch of tutorials to figure it all out, while with iMovie I just ran it and everything was intuitive and obvious.
I’m committed at this point, and will master it all eventually, since this is the only laptop I’m using now. Sink or swim! Bye, Apple!