you can try to find likeminded people on Mastodon (also currently on HN front page, an open source, federated twitter clone) or scuttlebut (imo more decentralized even, but quite focussed on solar punk in New Zealand) I guess. Also the Pirat Party (actual political party in case you don't know) uses a similar system IIRC.

And you can probably just start with the community around Decidim and work your way outwards to a wider community by participating in discussions and learning to know people.