These packages upgraded (though they seem no longer on Debian!). The upgrades would not play with opengl2 so plasma would no longer run. Downgrading to testing, due to partial removal from the repos, proved impossible. No more means to file bugs, either!
So I uninstalled them, went back to Nouveaux (which I might even prefer). Plasmashell is unstable, crashes and restarts, and multiple session will not work. Could live the a single-session if that be stable. There had been problems with firefox in nouveaux last year. What to do about all this?