@ryanjamurphy - Thanks for your help here! I’ll follow up on all your suggestions. I’m an early adopter/beta user for Coda and they have been fairly responsive (except @BenLee who is the moderator on that coda forum link you noted). And I’ll open a bug report here, but I suspect your intuition that it’s a Coda issue is correct – if it won’t work here, and it doesn’t seem to work in Incognito tabs (per the Coda link), and not in Obisidian docs, it seems to me they are doing something funky on their end. I’ll report back in case others are looking at the same problem.
Reporting back already…
[1] Like, you, I can’t get a valid Coda iframe to embed here.
[2] I can view a public Coda form in an Incognito window.
[3] I cannot view the exact same public Coda form in Obsidian
[4] Bug report is here