I donโt believe so. I just shifted my test user up to TL3, so itโs definitely not a TL restriction. Something about the invitation link itself seems broken. See below when accessing it through normal means (the link performs the same whether my user has access or not).
Unfortunately, these groups operate only via DMs, so thereโs no per-category marriage to rely on.
I think sharing an invitation link in a DM will be sufficient once we figure out why itโs not working 