Sports is definitely hard to have take off in these sorts of spaces, since sports are generally talked about much more amongst regular/casual users, than the more tech-savvy crowd who are willing to try these things out.
It’s the same on the biggest ActivityPub platform (Mastodon) - the really popular regular subjects such as sports and cars just don’t have a presence there.
Sepulchre is so good, it’s basically my happy place in OSRS and actually makes Agility a top tier skill in my opinion. I ended up getting 94 agility very early on my ironman just from how much I enjoyed it which set me up very nicely for so many things.
Wish we had more agility courses like sepulchre and maybe everyone would stop complaining about doing rooftops.