Yeah the disabling of the serial ports should have helped. You can speed it up a little by disabling the NetworkManager-wait-online.service as that is not needed at that point. It will save you a little time.
sudo systemctl disable NetworkManager-wait-online.service
You could also try reinstalling the kernel to regenerate everything after the major hardware change.
sudo eopkg install --reinstall linux-current(or linux-lts if you are using lts kernel)
