Interesting post and important topic, thank you.
Even though historical examples have their limitations when considering how humanity’s exodus will play out, I think we might be able to glean some useful insights from the history of Iceland. There, a colonization project (largely by individuals escaping growing state power in Norway) ultimately resulted to world’s oldest still-functioning parliament, the Althing.
Iceland might also offer some suggestions about how the culture of our space colonies might possibly develop. I’m not Icelander but I’ve been struck in the past by, for example, how extensive genealogical records and historical sagas seem to affect the culture — most Icelanders can easily trace their ancestry all the way to tenth century, and their national epics tell stories of their identifiable ancestors.