jwolanin
I personally use the standard keyboard and have to switch various languages constantly.
Instead of spell checker (System> Keyboard> Spell Checker – I always found the red line annoying, as well as the fact that you always have to go deep into the settings to change spell checker language), I simply work with text suggestions and auto correction (turn on System> Keyboard> On-screen keyboard> Keyboard settings> Text correction> Text suggestion and Auto-correction).
You can quickly switch between installed languages (Settings> System> Languages & region>System languages) by long pressing the space bar, which conveniently also automatically changes text suggestion and auto correction.
(It sounds more complicated than it actually is trying to explain it without pictures, sorry for that).
I used to be a Gboard swiper (you didn't even have to change the language, Gboard recognized and corrected it automatically), but after getting used to it, I'm not significantly slower with the standard keyboard and my minimalist self is quite happy I don't need to install another keyboard (I tried it and also found spell checking quality variing a lot depending on your language and the third party keyboard used).