Comment # 4 on bug 97618 from Dan Kegel

Installing from the padoka PPA did indeed solve my problem.
No warnings in /var/log/kern.log, either!
So fixed as of libgl1-mesa-dri 12.1~git1600912162600.546bc07~x~padoka0
et al.

(There are still 78 fails vs. 5984 passes, but IIRC that's less fails than
before.)