Federation - Compatibility with other *cord alternatives

I do not believe any of the platforms you listed have any form of federation support The only way would be to log into user accounts for puppet bridging which is unsupported and prone to breakage, and even then would provide poor federation support I'd recommend closing this issue, as it's unlikely that the other parties would be willing to work on that given the complexity (especially SpaceBar as it's a reimplementation, not a new protocol)