Unfortunately it took me a little bit to figure this out, but after having assigned a channel for inviting members in, the listing for Linux Enthusiast Group has been re-listed. It appears like you have to click on a completely unnecessary overflow menu hiding the edit button, which took more than ten minutes to figure out — big UI fail.
For people curious if there are alternative means to join our group, there were until spammers and bots made it untenable to maintain a presence on Matrix without tedious micro-management. Until we find somebody with more expertise than our current staff managing civility and cleanliness in our Matrix group, access to this group is discontinued indefinitely. Apologies to people who can't join in on our conversation otherwise due to Discord and other social media services rendered inaccessible in your region.