wow this looks really cool. It's a decentralised libre version of some of the features of keybase.
Keyoxide allows you to link accounts on various online services and platforms together, prove they belong to you and establish an online identity. This puts you, the internet citizen, in charge when it comes to defining who you are on the internet instead of large corporations.
Looks very cool in Firefox, Chrome etc.
Sidenote for Mac users:
You will at least need macOS High Sierra 10.13.6 with Safari 13. Give Tim all your money.
Sunbeam City is a anticapitalist, antifascist solarpunk instance that is run collectively.