I would love to do it this way but so far for any of my projects, github is the only platform that I received contributions (issues, code contributions, etc).
Unfortunately I feel this missing critical mass is a real sticking point for many small projects (think 10-100s of github ‘stars’). I hosted the projects simultaneously on other platforms and other projects exclusively on other platforms and never got engagement from the community except for a single heroic individual sending a patch per email.
I get that breaking this critical mass is part of the point and I am the dude complaining that my friends are all on whatsapp but it seems even more deeply entrenched here to me, starting with service-dependent issue collaboration. Only ways out I see currently are decentralised issue discussion à la sr.ht mailing lists, direct tracking in the repo like git-bug or federation/2-way mirroring of the centralised ones.
Until then, I don’t foresee this monopoly budging.