I believe the setting for this was disabled when solving https://github.com/brave/brave-browser/issues/512 (with https://github.com/brave/brave-core/pull/244). It's hard for me to tell if spelling corrections are coming from my operating system (macOS) or from Brave Core
browser-laptop supports multiple languages:

Still disabled in the latest release:

Still disabled for languages other than English (US) in release build (v0.58.18). +1 from Community:
https://community.brave.com/t/brave-spell-check-in-other-languages/41378
Still not working on 2020. Spell check in non-English dictionaries is a vital feature for me.
Same here: Version 1.4.96 Chromium: 80.0.3987.132 (Official Build) (64-bit)
I wonder what's more important in a modern browser: spelling support for human input or a crypto wallet?!
Is that issue fixed? I am not able to get spell suggestions for French but I have them for English.
Nope, still no German dictionary (and maybe others missing, too) .
Most helpful comment
Same here: Version 1.4.96 Chromium: 80.0.3987.132 (Official Build) (64-bit)
I wonder what's more important in a modern browser: spelling support for human input or a crypto wallet?!