WebID default serialization for WebID 2.x

There was a thread in August 2021 regarding the webid default
serialisation, that seems to have stalled, in the github area

Given that WebID 1.0 is still in use, I propose that we have a 1.x branch
that continues to support those using it

For future implementations, I propose that WebID 2.x:

1. Has a default serialization (MUST in the spec) -- this can be a point of
debate
2. What the default serialization should be for future versions

I call for a major version upgrade so that existing implementations can
continue to work, and because there are potential breaking changes

Given that (2) follows from (1) it would be good to solve (2) and get the
opinion of the group

What is view of the group on what should be the default serialization of a
webid?

My vote:  JSON(-LD) as default, including structured data islands which are
part of the JSON-LD 1.1 spec

Other opinions welcome!