Thanks all for your suggestions
Starting Xquartz didn't seem to help... and it looks like there is no option to allow all apps like the faq mentioned... that definitely seemed like a possible fix :(
(Took a screenshot:
https://imgur.com/a/L0Atn7f)
What's really weird is it was going through the "normal" flow the 1st time.
Aside from removing InkScape is there anything else I could wipe? Preferences etc/ places it writes to on install?
If I could get it to do a "clean" install maybe I can get that dialog to specify where X11 is back, and things will go normally...