To answer your question specifically, I'm used to "English (intl, with AltGr dead keys)" but in Linux Mint there are like 20 options. I was trying "US, intl, AltGr Unicode combining" or perhaps "US, intl, with dead keys" or such. (I've tried about a dozen in the last 2 days.) Instead of an apostrophe, they were generating what could become an accent mark, a stress mark or diacritic depending on the next letter. On "with AltGr dead keys" you must use right alt+apostrophe for that effect. (The quotation marks would do the same thing.)
Anyway, the keyboard lets me type things like þðßáœßðfhëü´6´^¨¼²³¤` with 2 buttons like shift to make a capital! This is good for German, Spanish and French, but Hungarian and Romanian require 3 buttons, then a 4th which is more tedious.
left alt shift 5 = ş ţ romanian
left alt shift 3 = ā lines for latin
left alt shift 2 = ű ő - hungarian long umlaut
On some keyboard layouts, pressing the quote mark starts a modifyer and then depending on the layout the following character is combined with the quote mark. Most English layouts don't include ś in this, but some Eastern European (?) languages use that character more often and so include them in this modifyer shortcut.
To answer your question specifically, I'm used to "English (intl, with AltGr dead keys)" but in Linux Mint there are like 20 options. I was trying "US, intl, AltGr Unicode combining" or perhaps "US, intl, with dead keys" or such. (I've tried about a dozen in the last 2 days.) Instead of an apostrophe, they were generating what could become an accent mark, a stress mark or diacritic depending on the next letter. On "with AltGr dead keys" you must use right alt+apostrophe for that effect. (The quotation marks would do the same thing.)
Anyway, the keyboard lets me type things like þðßáœßðfhëü´6´^¨¼²³¤` with 2 buttons like shift to make a capital! This is good for German, Spanish and French, but Hungarian and Romanian require 3 buttons, then a 4th which is more tedious. left alt shift 5 = ş ţ romanian left alt shift 3 = ā lines for latin left alt shift 2 = ű ő - hungarian long umlaut
If you really want to learn about ways to enter writing systems, this is a wild ride: https://en.wikipedia.org/wiki/Chinese_input_methods_for_comp...