util-linux 2.39 switched to the new mount kernel API (https://github.com/util-linux/util-linux/blob/master/Documentation/releases/v2.39-ReleaseNotes), but unfortunately this is still quite error prone.

The current openQA failure is caused in transactional-update, which is calling mnt_context_set_mflags to set certain flags. The behaviour of this function changed: Previously the context of the existing filesystem would be reused, now the options are stored separately in the context and everything is reset if options were not set explicitly via mnt_context_set_options. It's not clear to me whether this really was an intentional change.

I'll adapt transactional-update accordingly, but I'll also open an upstream bug report.

Apart from that it's currently probably better to use the --disable-libmount-mountfd-support configuration option according to https://github.com/util-linux/util-linux/issues/2287#issuecomment-1576640373 - this limitation will also hit us, not only with transactional-update when using several layers, but also when using containers.