Some in the movement advocate for borderlessness. I think it’s kind of utopian (in the negative sense of the word).
I agree that the modern conception of nation-states is problematic. In regard to the anticipated bioregional entities I tend to use the words “sovereignty” or “commonwealth” instead. Maybe there’s a better term.
For the sake of a truly participatory form of democracy, the relevant jurisdiction must be smaller than our current nation-states. Kirkpatrick Sale talks about that in his book: Human Scale.
But democracy exists within some kind of entity. And communitarian integrity requires borders. Encroachment must be anathema (look at Russia-Ukraine, Israel-Palestine, etc.)
For example: An ecovillage figures to have a land-specific place-of-identification. The idea is a stable group of familiar people sustaining life together, dwelling in a particular place on earth. The broader particular-place-of-identification is the bioregion.
A sense of particular territory was vital to indigenous peoples. Their borders were not rigid as are those of our modern nation-states, but they were, nonetheless, acknowledged. Between tribes there were rarely wars (in the horribly destructive sense that we know wars), but there was much in the way of skirmishing … and most of that skirmishing had to do with territorial boundaries (fundamental to cultural identity).
In the Wikipedia article: Cascadia (independence movement) … there’s this: “the Cascadia Department of Bioregion, a 501(c)3 non-profit, seeks to build a bioregionalist network as an alternative to the nation-state structure.”