@andstatus At the present time there is no alternative which can possibly unite the free web. The only way I can see to move forward is for projects to support multiple protocols into the foreseeable future.

There are some interesting developments in the works. Unlike ActivityPub, I believe that discussing any alternatives before there are solid specifications and tested implementations would be foolish.

I will note that the basis for ActivityPub is ActivityStreams2, which is a well designed and extensible specification. It is however merely a serialisation and not a transfer protocol. If you paired ActivityStreams2 with a solid transport protocol you would have something useful. So supporting ActivityStreams2 is still a good idea. Unfortunately, ActivityPub frequently confuses data and transport and puts a lot of additional constraints on the data which aren't present in AS2. Keeping the AP data restrictions separated from the lower AS2 data layer so that the transport layer can be cleanly replaced is a bit of a challenge.