snappy and/or ceph: snappy-1.1.9 breaks ceph

The update of snappy from 1.1.8-r2 to 1.1.9-r0 breaks ceph: After the update, ceph complains that "OSD(s) have broken BlueStore compression", and ceph health detail says that the reason for this is that ceph is "unable to load:snappy".

Underlying cause is that snappy version 1.1.9 removed support for RTTI, which apparently ceph needs - see https://tracker.ceph.com/issues/53060. And judging from the ceph ticket, snappy upstream is unlikely to add it back in.

I tried to manually pin snappy to version 1.1.8 to roll back to the last working version, but that conflicts with ceph.