From my experience it is much worse than it used to be 5 years ago. I have been writing English, French, and to a lesser extent German on an iPhone since ~2008. Initially, the dumb autocorrect would just correct to the closer word in the dictionary corresponding to the current keyboard, but over time it would pick up more and more words I used regularly. At some point around 2018 or so, it was nearly flawless. I think it changed the dictionary depending on the language or the sentence, because I had different suggestions for the same mistyped word in the same document. Also, I assume that by then my personal dictionary was quite extensive.

And then they bragged about a new machine-learning improved keyboard and it went downhill. First, all keyboards became monolingual, which was a 10-years regression. And even in that language, it was very flakey. They added multi-language keyboards somewhat recently and it got slightly better, except that for some reason it changes the keyboard back to the English-only one regularly for no reason I can see.

It is maddening. For a couple of years it was fantastic.

And that’s not the worst. On the Apple Watch not only is the multilingual keyboard completely broken, but worse than that: if you change the language of the keyboard by long pressing the space button it shows the new language, but the autocorrect proceeds to just ignore it completely and autocorrects everything as if I were typing in the system language rather than the one I selected.

And contrary to the iPhone you can’t even disable autocorrect! This + the super-aggressive autocorrect of watchOS (the screen is small after all so you are likely to make a mistake and we better fix it automatically!) makes it an absolute NIGHTMARE to type on an Apple Watch in multiple languages. Your only option is to use speech to type because that one for some reason works when you change the language whereas the keyboard doesn’t care.

Edit: the language switch bug on watchOS seems to have finally been fixed on watchOS 26.1. The bug was already long present on watchOS 11, so not something that watchOS 26 introduced.

This scarily aligns with my experience. 2018 was the golden age for keyboards for whatever reason.

Completely agreed. Apple seriously regressed the multi-lingual experience. They probably have a model per language. If you have to mix languages in a sentence, well, good luck!