Thanks. I did try again to install all 3 kexts with MB, but it still didn't work. I wiped the system and started to reinstall. But, once I booted from the UniBeast drive and before I started the OS install, I opened the terminal and pinged my router, and it was working, so I knew it wasn't my hardware. I then did the clean install.
Once it was up, I ran MB again and installed AppleIntel and Atheros, but upon reboot, networking still didn't work. I popped the UniBeast drive back in, mounted its EFI and looked at what kexts were where, and compared to the EFI on the boot drive.
I found that MB had installed the kexts into S/L/E, but they were not in EFI/Clover/Kexts. I copied all the kexts, and dropped them in EFI/Clover/Kexts/Other and rebooted, and it all seemed to work.
My wondering is: Why did MB for Yosemite create a clover folder in the EFI? Wasn't MB still using Chimera then?
Also, I was feeling cocky, so I downloaded the Mojave installer and ran that - 30 min later, the system was booting into Mojave with no major issues. I'm gonna push on the edges a little more tomorrow when I get into work to see if there's anything I need that's not working, but for the moment, I'm basking in the glow of a nice (and somewhat easily) working system.
thanks!