I guess I can remap middle-click to left-click using the wayland equivalent of xinput from a shell script or something. The apparent-FF-crash story described by johnmaguire and eddyb sounds very much like another thing I believe is happening on my notebook. Between these fuckups and the general alienation going on in Linux land (wayland, snaps/flatpack, systemd) I've got to say I'm not enthusiastic to go through those chores and teething probs just to get the same-old gui apps like Inkscape and GIMP (plus FF/Thunderbird) running, so right now I'm leaning to go back to Mac OS more than ever (used Mac OS on and off from 2003 to 2016).