It figures after living with this for a week and now posting here I figure it out an hour later. Settings > Keyboard > Keyboard Shortcuts > Modifier Keys - the globe key was set to "No Action". Setting it back to "Globe" took care of it, seems like it controls everything on Fn.
This is distinct from the Settings > Keyboard > Press globe key to... which can be set to Do Nothing and have Fn key work as I expected (forward delete, function keys, etc.)
Sorry for the noise, hope this helps someone.
aclysma
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