Its immediate focus, at least in the US, is sovereignty of indigenous nations where each nation’s land would be defined by current federally recognized reservations which indigenous folk occupy right now. Past that would be working to reverse legislation which has broken up this land, deny resources, repress indigenous culture for those living off reservation etc. I think the discussion of reparations should be had as well but realistically that’s probably a bit far off.
Ideally, in a world where western governments acted in good faith and with care for human life, we would be able to work directly towards returning land traditionally occupied by indigenous folk across the world to them as each peoples/nation saw fit, but realistically this takes the form of returning full sovereignty of what little land is officially recognized as belonging to each indigenous group, and then working from there through community organization, protesting, lobbying etc. to continue working to advance the rights of indigenous folk and repay in some way what has been stolen from them
To your last question, again in the context of the US, many indigenous groups already have their own governments where citizenship is determined how they see fit, some are stricter and go off of the standard of blood quanta which was put in place by the US govt. centuries ago, some go off descent, while others welcome anyone who has a clear cultural connection to the people. Part of returning sovereignty to these nations is allowing them to define citizenship however they see fit.