I have only seen this warning in the iOS version of Brave.
Can someone at Brave corporate contact them and get brave on the list of approved browsers. I would hate to have to sw to another browser for just one site.
My best guest is because eBay saw Brave as an “outdated” version of Firefox. Brave for iOS is using Firefox user agent and it seems it’s a few version behind the latest Firefox version.
The only solution is waiting for Brave to update the user agent. cc @sriram@anon1255531 on this.