The only limitation is the keyboard on the device you are using.

Thes reminds me of an old joke.
If a person who speaks 3 languages is called trilingual, and someone who speaks 2 languages is call bilingual, what do you call someone who speaks only one language? American.

If you are using a laptop in a foreign country there is 100% chance the keyboard will be bilingual. Usually there is a switch near the space bar.
Every non-English speaker’s phone has a small “world” symbol near the spacebar that will switch between languages so you can be mobile as well. .

Ok but why would the switch language options in Google search (one right under the search bar and another at the very bottom page) or the Gmail sign page not take care of it?

@LuckyGuy The keyboards I have known have Alt and Alt car on either side of the space bar.