[Wubdidu]

I've been using first party isolation for quite a while on desktop and Android and the only websites I experienced issues with are the Atlassian login and the Trello GitHub powerup.

Everything else, including tons of single sign in/OAuth websites, work without any issue.

[OJFord]

Yep, ditto Atlassian. There's a big thread of people complaining about it on their forums too.

Unfortunately of course it'll always be a minority, and won't affect whether even those people (have to) use Jira or whatever, so not really any incentive for Atlassian to fix it.