I said in another comment that the upgrade was smooth, until I tried to use the Compose key. (I use it all the time.) It was just a matter of reconfiguring stuff:

• revert input method from iBus to XIM
• configure the XKB options to specify where the Compose key is.

Then it’s working again. It used to show the sequence of keys I was typing, until I finished it, now it isn’t any more, but… you know what, not a big deal.