@mcc There's no way to disable 1p-isolate on a per-site basis or anything. It's global.

I have not run into anything that seems to be broken by it. Normal SSO-type workflows nowadays know they have to pass data thru redirects and stuff rather than relying on being able to access cross-domain cookie state.

But if you're concerned, using a weaker tracking protection that can be turned off per-site might be a better choice for you. You cannot switch later without losing all your saved cookies (because of how the re-scoping works; actually I think the scoped ones are still there, but scoped in a way they'll never get used unless you switch 1p-isolate back to how it was set before).