Office365 Groups <-> Outlook Groups

Im relatively new to the Office365 landscape. When I create a group in O365, I can use that group immediately in Teams - which is swell. When looking into the Exchange admin center, the group is also visible ... which is strange, because my Google-search odyssey tells me relatively uniformly that these are two systems that don't necessarily work together (at least, not without PowerShell expertise)...

Anyway, in Outlook, searching for this public group made in O365, i actually find it - also write mails to it. I can even show (right click Groups -> search -> show) the mails that have been sent. What i cant do, though, is add this group to my Outlook Groups .... at least, for no longer than a fraction of a second.
After clicking on 'join' and having it show up in my Groups - it immediately disappears. Exchange AC tells me that I'm apart of the group the entire time and yet, in Outlook itself, I can search for the group, click join and get thrown out ad infinitum.

So .... in order for this group to stop disappearing I need to use PowerShell? I'm kind of finding that hard to believe...

To sum up - I can see the O365 created Group in Exchange, write mails to it and even see its inbox over the group-search functionality... and even join the group and in Exchange AC be shown as having joined the grou - but it disappears almost immediately in Outlook and I can join ad infinitum ...

Whats going on? Is PowerShell really the thing I need to do here?