.io has been used as a sort of general-purpose tld to signal sort of… I dunno, hip, dev-focused sites, right? It is at least slightly less novel than gg.
Agree, but it’s important to point out that .gg grew popular in the gaming crowd because “gg” in gaming means “good game”. It’s used in-game in the chat by many players of online multiplayer games as a way of thanking each other after a match. It can be used sincerely or it can also be used sarcastically but in the latter case you’d typically say “ggez” as a taunt implying that the win was easy (“ez”) because you are more skilled than your opposing team.
And for .io of course that one is/was popular among tech companies because it looks similar to “I/O” (input/output).