Why isn't my network card discovered and enabled on boot?

I assume this is not a cloud-init instance. If that is incorrect, please stop and tell us in the comments.

Let’s follow the instructions in the file. Please open a terminal and do:

sudo -i
echo “network: {config: disabled}”  >  /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg 
nano /etc/netplan/*.yaml

Replace the line eth0 with enx0017f700a9d6. Netplan is very specific about spacing, indentation, etc. so please proofread carefully twice.

Save (Ctrl+o followed by Enter) and exit (Ctrl+x followed by Enter) the text editor nano.

Follow with:

netplan generate
netplan apply
exit

You should be all set.