Ahem. Totally not me. cough Nothing to see here.
Ok, now I'm curious. What did the network look like? Was everything mostly normal, but you just didn't have an IPv4 for the router itself? Did you have to use console to get in, or did ssh to IPv6 work?
A paperclip reset did the trick. And then I made sure not to repeat my boneheaded mistake.
Er, I mean, "my friend" made sure not to repeat "his" boneheaded mistake. Yeah, that's it.
Paperclip was way to “noob” easy way out for “your friend”.
If you (your friend) want to be a level 1 Pro you must connect to it and change the network config back and reload and you are online again.
Like when I away from home made a remote desktop connection to a raspberry pi server (with Ubuntu Server with desktop) through the VPN tunnel connected to the router.
And when I upgraded the server I lost the remote desktop connection after it had done the service restart.
I had to think a while and then I downloaded a ssh client and I was able to connect to the server through ssh and made a complete reboot of the server and hoped for the best.
And it actually worked, I was able to connect to the remote desktop again after the ssh initiated reboot.
Oh yes. Been there, done that. It's oh, so easy.
These days I have a separate out-of-band connection through a third ISP, which costs me a few pennies each month, and which is there solely as a back door in case I totally screw things up.
There are so many strange unknown holes to fall down into when doing this hobby!
And when we screw it up, it is often on a little higher level of problem😅
All my IRL friends don’t understand how I can find it interesting when these things happens and then tries to solve the problem, they mostly get angry and throw out the router as broken beyond repair if something like this happens.
I had a fun one a while back... despite working on a VLAN for an experiment and keeping the standard lan unchanged and theoretically functional, I managed to get locked out with what turned out to be a corner case that caused dnsmasq to error out.