Is there really no official project reactor upgrade guide from v2 to v3?

I’ve searched far and wide, even using waybackmachine, but I’ve had no luck finding any upgrade path documentation from v2 to v3 (v2.0.6.RELEASE to v3.5.15, to be more precise).
Now, I’m aware that I’m coming in a bit late with this question, given that the first v3 came out somewhere in 2017, but the current version is still v3, so I guess it shouldn’t be too late.

For some reason the official GH repo no longer contains pre-v3 tags/branches, so I initially assumed that the repo changed between v2 and v3, but I do see in waybackmachine that there used to be several v2.5.0.Mx tags back in November 2017. Is there a place I can get the v2 source code, so I can clone it and analyze in Idea locally?

The best resource I’ve found so far is this GH issue comment, but I have several other questions.

Specifically, what do I use in v3 instead of these v2 classes:

1. reactor.core.Dispatcher
2. reactor.core.dispatch.SynchronousDispatcher
3. reactor.core.dispatch.RingBufferDispatcher
4. reactor.core.processor.RingBufferProcessor (the comment I linked to above says reactor.core.publisher.TopicProcessor, but that too has since been removed)
5. reactor.rx.action.Action
6. reactor.rx.stream.GroupedStream (I assume reactor.core.publisher.GroupedFlux, since Stream -> Flux, but what do I use instead of GroupedStream.lift?

Thanks.