Hi, so I usually use the US/International keyboard layout (mobile/android,heliboard) However this doesn’t let me write many European languages, even those using the latin script. It’s honestly terrible. How do I get the Polish L and the C and S with an upside down ^ type thing on it from slovenian? halp
On Linux/Unix (not sure about other platforms), you can configure a “Compose key” (people usually use something like the Menu key, or the right Alt key).
You can then hit that Compose key, followed by multiple other keys and they will be combined into a character, usually roughly relating to the shapes.
etc. There’s a big table somewhere where all these are defined.
On android keyboards you can hold down the letter and get a list of “alternative” letters (seems to depend on the keyboard and keyboard layout configured what you get), you can also configure multiple languages/keyboards and then switch between them, by holding the spacebar.