<iframe> embed doesn't work on Firefox with strict privacy settings (cookies)

https://forum.torproject.org/t/snowflake-addon-in-firefox-has-stopped-working/16590

The snowflake plugin for Firefox has stopped working over the last couple of days when I’ve tried to enable it, for example by going to
relay.love
. It’s not just them, I’ve got that plugin on a site I control and it doesn’t connect when I browse to my own site, either. Both used to work properly.
Don’t know if something needs to be done to fix this . . ? Nothing has changed at my end that I’m aware of.

To be precise, are you talking about the add-on the the “embed on a site” version?

Because indeed, the embed doesn’t work on https://relay.love/. When you try to toggle the switch, you get an error: Cookie “snowflake-allow” has been rejected because it is foreign and does not have the “Partitioned“ attribute..
Probably has to do with third-party cookie protection.