Sometimes there are network issues to the debian site, perhaps during maintenance and such. Have you tried this again?
Also, on the FC34 system, is it connected via hardwire ethernet to the router or are you using a Wireless connection. If it is wireless, you might have to route that as well.
On the PB, you might want to try this:
https://github.com/RobertCNelson/boot-scripts/blob/master/network/doc-debian-setup.md
If you haven’t yet, have a look at the following:
https://forum.digikey.com/t/how-to-set-nat-on-beaglebone-black/4516
Also, there might be something you can be pick up from the following thread on the old forum.
https://forum.beagleboard.org/t/can-not-connect-via-usb/2038/39?page=2
You’ll have to do the translation from Debian to FC34 though.
Jon