In MuseScore3 we had minim, crotchet, quaver, bar and all the other British terms. In MuseScore4 we appear to have only the American terms half-note, quarter-note, measure etc. I hope it won't be too long until we get an update with names that we Brits are used to.
That should be the case already.
Make sure you're using the British English language settings
Menu path: Edit > Preferences > General > Languages > choose English (GB)