Hi, John.
Be sure the ethernet adapter is enabled in the BIOS/UEFI. It’s under Advanced >> Onboard Devices. I’m not sure, but I think the default is disabled. No, I can’t imagine why disabled might be the default.
After following the instructions from @Jeremy31, as I reported in [ RTL8125 2.5GbE Ethernet port not working in Ubuntu 24.04 ], my ethernet started working immediately, and it has worked fine for about three months, and then it quit again last week. I did not do any of those recommended DKMS things because it was working.
I also did not do any of those things you describe with “I’ve edited /etc/netplan/50-cloud-init.yaml” and renaming your ethernet connection, and I have no idea if your problem might be in those things.
I think I understand that the DKMS method is recommended because then system updates won’t break the fix I installed, but I haven’t tested that yet.
I noticed that you and I have identical hardware, and essentially identical ethernet problems with Ubuntu 24.04.x. What you probably don’t know is that I’ve filed several support cases with ASUS and they have never replied with any helpful information, only to acknowledge that they know about the problem.
I only have time to work on my system intermittently, and I don’t have any urgent need for it, so I can’t say when I will work on it again, but I will report if I discover anything interesting, and I hope you will too.
I think I will install Ubuntu 25.04 ASAP; I think I read somewhere that that might fix the problem, and if it does, then I think I will just do a clean install at that point and hope this problem is behind us.
Jim