The solution? Move off the 64 bit Raspberry Pi OS and install Ubuntu. Everything below is now just for history and context :)
Every time I update my Pi, whether it be an kernel update or due to something goofy I do, it refuses to be accessible via ssh after it boots back up.
And everytime I bring it back to my desk, it just works.
And when I put it back into its niche, by the door, it continues to work.
But inevitably, sooner or later, comes a reboot, and we’re back to being inaccessible.
No ssh, no plex, no network.
The other Pi, my old 3 series, keeps chugging along like a champ in the meanwhile.
This was driving me up the wall.
So I got to thinking, and I realised, I was running the 64 bit edition of the Raspberry Pi OS.
And then I got to thinking some more, hmm, this is not a mature os. What if, it might be buggy? Or what if, something I do, is tripping it up the wrong way?
Logically then, that meant the network stack, or the network interface, or the port itself.
Because everytime I brought the Pi in, to where my desktop is, I connect it to a switch (that connects to my upstream router).
And then when I take it back, it changes back to connecting to the router directly.
So the next time it borked, I put the Pi off, then turned the router off and on and then finally, put the Pi back on.
And that did the trick.
I tried it again this morning, when the Pi went offline, after another update. The heuristic still holds!
I’m sure, I could go digging further to find the root cause, (dhcp release renew not happening correctly?), this just lets me get on with my life and I’m happy :)