Comment 4 for bug 1845314

3. How we could fix it?

Well, given the data I posted above, my *guess* is that we could safely ignore the udevadm non-zero exit status in the udisks2 postinst script with something like this:

if [ "$1" = "configure" ]; then
    # we ship udev rules, so trigger an update
    udevadm trigger --subsystem-match=block --action=change || true
fi

Note the final "|| true". In case the conjecture I just made above is correct, I prepared a modified udisks2 package in a PPA which doesn't fail to install:
https://launchpad.net/~panfaust/+archive/ubuntu/udisks2

If the conjecture I made and/or proposed fix are wrong, I hope at least the data I provided leads to the correct solution.

Regards.