and GNOME 3 too

This must be BS or a regional thing. All the RCA ports I’ve seen in North America are labeled L and R, not L+R and L-R.

I think the biggest cost will be image/video storage. The text takes very little space in today’s standards. The good thing is that symmetric fibre internet connections are becoming more common so it may be possible for members of the instance to contribute unused disk space to help with its image/video storage. This plus limiting the image/video sizes (and maybe forbidding video uploads altogether) will allow the instances to scale with user count.