It was odd. But I took the Ethernet cable out, went via WiFi, games worked. Plugged cable back in and it still worked. A few people on Reddit had this issue at the same time as me, so maybe it was a brief outage or something. But it’s good to know this for a next time.
If it makes you feel better, I had to do a factory reset on my Halo XSX because of some oddities with games running from the internal SSD. For the future, if you ever have to, just back up your settings and games to an external drive and the on-boarding process is easier than setting up a new Switch (no joke, and having just set up a new Switch 2 as well, I have a wee bit of recent-familiarity with both lol).