Any keyboard incapable of simultaneously (without switching) support multiple languages is a deal breaker for me... Unfortunately it seems like gboard is the only one that supports this
It does, and it really annoys me! I use English 99% of the time, but it decides I’m using another language about 50% of the time I start a new sentence! There doesn’t seem to be a way to turn it off, either.
I’m on iPhone, using English and Dutch with the built in keyboard and it’s pretty seamless. Basically the layout doesn’t change (it’s always qwerty) but it will detect the language I’m typing and spell check for that language. That might only be possible/easy for languages with a (mostly) common alphabet.
Edit: there’s also a button to force the language if I want to override it. It also seems to read the text on screen or remember what apps use what language as it will auto-select the right language most of the time.
It works when using multiple languages that share the same writing system (the Latin alphabet). It means that you have a single keyboard, but the words that swipe or auto complete are from more than one language; generally the predictive nature means that when you switch languages it's pretty good at predicting future words are from the same language.
It also means things like you get all the diacritics from all of the languages when you long press.
I was studying French, while also working with several Polish people, so I set my keyboard to simultaneously English, French, and Polish, and then I was able to do French lessons without switching, and also able to write my Polish coworkers names easily.
