I’m going to go at it sideways, because while I think if efforts to date succeed (and sure is looking that way), we aren’t nearly as likely to have a hot civil war. I think it as likely (more honestly) that if things continue the way they have been that after a de-legitimized Republican seizes power, that each state will largely go their own way, chosing to ignore orders / not enforce orders from the top. Purple states will be too internally divided to do anything, majority states will be fighting along urban/rural lines and other divides, and the military itself will be divided (if less so) but probably just a bit too vulnerable to it’s supply chains and fear of local disruption, especially in light of a large number of deserters giving support to either side based on personal preferences - so they’ll wait for ‘clear orders’.
None of which will matter, because if it gets to this stage, the nationwide economy is going to collapse. Supply issues? Oh heck yeah, interstate commerce will be one of the early losses. Who goes to work when they’re not sure they’ll get paid, if they need to pay taxes to a corrupt government, or worried their neighbor is going to burn down their house for having put a Biden flag up in a prior election? So, rather than a Civil war with 2 sides, I suspect we’ll just collapse into a failed state, with a half dozen or more loose alliances, none of which can do too much because they’re all to damn heavily armed (all it takes is 1-2 nuclear weapons available and even the smallest faction can play the North Korea Game HOME EDITION).
At this point, the military might try a coupe to restore order, but I think it will be too little, too late, as trust will be long since lost, but with a popular enough leader, it might work. Still leaves us will a dozen small wars going on and an utter collapse of societal norms.
As for preparing, I’m too old to fight, too young and poor to retire/flee, and so if it gets to the end-game, I’ll probably be riding it out in my deeply purple state until one of the above issues ends up getting me killed.
I mean I could try to utilize the Right to Return, and I do have (quite a lot) of Israeli family, but don’t see things there being particularly better in these circumstances, as once the US collapses, things will escalate quite quickly there as well.