Today I learned Brave browser doesn't send "Brave" in its user-agent string because they don't want websites sending messages to their users explaining why Brave is a terrible choice of browser.

They send it in a non-standard header and make a non-standard JavaScript API available to "detect" Brave users... but if you as a webmaster actually use it to send messages to your users explaining why Brave is a terrible choice of browser, they'll silently deactivate it when browsing your site.

Legit.