To be clear, I suck at ultrarunning -- I can do 100km runs but I usually place near the end. What I love about it is that nearly anyone can run an ultra if they simply train long enough... It's why I call my personal performance blog "10 Million Steps" -- if you do enough steps, you can usually do an ultra (barring any deeper health issues). It's almost always about consistency... and I bet you are a better SWE than you are willing to admit because you sound very consistent. :)
A lot of professional coaches come from this space. I highly recommend following Steve Magness[1] and Brad Stulberg[2] on Twitter...
Alas, no communities that I know of.
If you're thinking of starting one or would be up to chatting about organizing something, I'd be 100% down to do so. You can reach me at w --at-- phaseai --dot-- com
[1] https://10millionsteps.com/