Our web host migrated our account to a different server today and chose to do it during the day rather than overnight. Not good for my wife's clients but at least it meant I could deal with issues immediately rather than waking up to problems tomorrow.
As always happens when they change things, the database encoding went screwy so I have had to explicitly set the encoding for the connection. It's still causing a problem including emoji in posts so I need to investigate further. (Fixed!)
They also decided to change the PHP version rather than respect what was set on the old server. I had a moment of panic until I checked the error logs and realised what the problem was. 😅
