Fixing USB-C on Dell XPS randomly stopping working....

Symptoms:

• After a sleep/hibernate, USB-C will totally stop working on 1 or more ports. Some may continue to work, others may not (e.g. two on the left side of laptop don't, but one on the right does).
• Plugging devices in doesn't bring anything up in DMESG.

Solution:

No idea why, but from a Reddit post, found that running the command 'fwupdmgr' causes something to initialise and restart. I had two screens plugged in on USB-C at the time (not working), and they magically came to life.