Is there a platform where I can form a social group that permits invited members to join using any email address they have?

I want to put together a group of about 25 people for a class reunion and be able to share files like old class pictures.
Previously, Yahoo groups permitted anyone to form a group and invite members with any email address. That was perfect! Unfortunately they have changed terms of service and now require everyone to have a yahoo email address. Google has groups but they also require everyone to have gmail accounts.
Facebook has pages but they, too, require everyone to have a FB account – and it is too intrusive

I want a site that will allow me to form a group, and send invitations to any email address, not just theirs.
Yahoo groups did this for 20 years but alas, time marches on.

Since we are “old”, some folks have addresses from aol, outlook, yahoo, gmail, company addresses, etc. I do not want to force them to open new accounts. They will never check them. And half the group can’t be bothered with FB.

Right now we are using an email with all 25 names on it. That works but is not convenient. I’d like to be able to post a calendar, and class pictures and maybe a few report cards. :-)

Surely there is something out there but I can’t find it. Please Help!