Domainless SAML/WS-Fed identity provider user cannot login to the MS Teams desktop app

Hi,

My tenant is configured with a domainless SAML/WS-Fed identity provider. We've invited a user with UPN "******@mypersonaldomain.com" and the invitation was redeemed successfully. This user was then invited to and has access to a Sharepoint site. The user was also invited for a MS Teams team and could access it through the MS Teams website. This all works because the URL's are scoped to my tenant.

However, the user cannot login to the MS Teams desktop application because the login process for the desktop app does not seem to support a login scoped to a tenant. Even if opening a URL like

https://teams.microsoft.com/l/team/19snipsnip/conversations?tenantId=<mytenantid>

Anyone experiencing the same issue or maybe even have a solution?

Thanks,

Peter