I was digging up old layers of the Internet and found out about old (well, late 90s, early 2000s) texts by Bruce Sterling who mentioned his Viridian notes where he describes something very close to a solarpunk movement (sustainability focused tech and social changes). It is fun to read because some have very strong cyberpunkish vibes but with the twist that cyberpunk describes the world we are in right now and viridian is the world we want.
It led me to learn that there is a label that more or less matches solarpunk in political theory: Bright Green Environmentalism
This is a huge corpus of text and I obviously disagree with some things, and the 1999 vibes of promoting at the same time intense air travel (for multi-culturalism) and sustainability sounds a bit tone-deaf, but I find it interesting to dive in with a tolerant curiosity.
(Dig that 1999 GIF btw!)
Nothing in the article about solarpunk describes such protections nor in the manifesto pinned here, mere declarations of intention. Don't get me wrong, it is obvious to me that a solarpunk future is deeply anti-authoritarian but it is not only that.
This label describes the solarpunk position on the environmentalist cluster: neither light green (let's just make ecology a consumerist trend) or dark green (We can't change anything unless we abolish capitalism first, we are likely doomed anyway).
You are right that it does not state its position on the authoritarian axis but I find it fairly obvious that "radical social changes towards sustainability" and "more widely distributed social innovations" do not include the promotion of "innovations" like authoritarian states.
I think you need to read the manifesto again more carefully if you don't see how it was quite intentionally designed to be anti-authoritarian. You simply can't have a "Solarpunk" authoritarian state, it would be a direct contradiction of the terms. The same is not true about "bright green environmentalism" despite the overall progressive terms that are used to describe the idea.
Like I said it describes intentions, not protection mechanisms.
Obviously you can't describe that in detail in a manifesto, but it makes it clear that anything not anti-authoritarian can not be called Solarpunk without completely perverting the idea. That is a form of protection against co-optation of ideas.