For all TootWorkers who want to verify their Mastodon account on their Keybase profile. It's a little finicky with our setup here since Okta does not forward links properly.
But all you have to do is use the #keybase command-line utility and do:
$ keybase prove toot.thoughtworks.com <your-username>
Then copy the given URL and paste it into a window where this instance is already open and visible. That worked for me.