How to fix lan config in extremis?

How does one un-hose one’s lan config?
I created an invalid wlan configuration and to my horror discovered that the ethernet stopped working too. There is a warning to that effect in the docs but the implication dawned on me too late.
Since my HA instance runs off an external ssd, Is there a file I can edit by hand to restore my Ethernet functionality?
You wouldn’t believe how grateful I’d be if someone could tell me.
Thanks in advance!
JDA