Nowadays there is very little reason for a Facegroup to be public.
One other downside of a public group is that all your friends will see your group posts and comments in their feed. Most people wouldn’t want to see content about niche hobbies they don’t care about so I’m never active in the public groups for this reason, and I know a lot of people feel the same way.
While you’re at it, you might consider dropping permanently the “Videos” button in that same menu - the site linked to, “SOTA TV”, has had no updates since 2013. That’s 9 years out of date by my reckoning, but I’m getting on in years, so I might have misencalculamated…
Perhaps it is because I only occasionally log in to facebook and have my privacy and security settings set to max, but I’ve actually never seen any of these types of posts in the group.
Yes, this is the exact reason I rarely like or comment in public groups - these likes/comments then appear in your friends’ timeline. Not that I don’t want them to know that I enjoy SOTA, but more that I don’t want to clog up their feed with stuff they have almost certainly have no interest in. I’ve unfollowed friends in the past due to them constantly commenting/liking/sharing stuff I don’t want to see or know about.
I was a member of the Free Expression group, but I was always uneasy about, such a weird title, I think I left after seeing a rant on there about something, realising it wasn’t really about SOTA activations. I have to admit to joining the other one due to the Facebook link. Btw the Free Expression group are already ranting about this thread and copying and posting!
This has happened on a few other facebook pages. Facebook have changed groups recently so you can be a member or just participate with out being a member. Probably something in the settings might stop it.