For me it’s 1.15. I really did not care for the nether update, but I think this is an unpopular opinion. Unfortunately doing modding on this specific version is not great. 1.12.2 obviously has the best modding support, but I really liked the 1.13 aquatic update.
I just think a place dedicated to looking for others to play with is a good idea, so you can quickly find posts on the topic of looking for others to play with.