isn't this the right place? I started with the sponge forge site where I get the downloads. http://files.minecraftforge.net/maven/org/spongepowered/spongeforge/index_1.12.2.html
If not, do let me know where else to post it. :-)
EDIT: I just found the main sponge page and posted here: https://forums.spongepowered.org/t/exception-occurred-during-a-phasestate-on-startup/21845