How does pattern matching work in grep for accented characters (eg. á, è, ò)

What characters match the following regex :

^[a-zA-Z]$

Specifically, should characters with accents (eg. á, è, ò) match this regex? Or just 26 lower and upper case alphabets? I have tried to [check this](https://regex101.com/r/KN4fgg/1) in an online regex, and accented characters did not match. When I tried it out with grep on my Linux (Ubuntu) machine it **did match** the accented characters. While rg(ripgrep) **did not match** it. I can match accented characters with rg using [A-zÀ-ÿ] But is there a way to exclude accented characters from matching in grep? PS: [This](https://unix.stackexchange.com/questions/505477/grep-to-find-a-word-matching-a-specific-pattern-and-ignore-accents) question talks about how accented chars can be included, not excluded.