Members of the military take an oath to uphold and defend the Constitution, not whatever government happens to be in power. Whoever is sworn into office on January 20, 2021 will be the commander-in-chief of the armed forces.
With the very high likelihood that Amy Coney Barrett will be on the bench by Election Day, an election that goes to the Supreme Court will result in more hard feelings.
I think that fears of a civil war are exaggerated. Neither side is well enough organized to wage a serious campaign.
There are probably well over 100 million gun owners in the United States. They span the entire political spectrum, but conservatives are more likely to be gun owners than liberals. Military veterans are more likely to be gun owners that most other demographic groups.
However, most gun owners aren't militant in the sense of an insurrection or civil war. I would honestly be surprised if even a half-million gun owners would as answer a call from Trump to resist an orderly change of Presidents.
There is probably more to fear from small groups engaging in disruption, sabotage, or domestic terrorism than there is from conservative, pro-Trump activists.
The United States is not now, never was, and was never intended to be, a democracy. It is a federated republic of 50 sovereign states, which have an unusual amount of power. Hillary Clinton's 2016 plurality was the result of run-ups in two states: California and New York. Trump won the popular vote (by a larger margin) in the remaining 48. That is based on the state-by-state certified results of the election.
The Electoral College worked exactly as intended.
For some reason, whether it's ignorance, laziness, or stupidity, those who condemn the Electoral College have never figured out that the solution lies within the states, not the federal government or the Constitution.
The states are free to chose any method they wish to apportion electors. Apportioning them based on the popular vote within the state, instead of the winner-takes-all system used by every state except Maine and Nebraska, would be a much better system. It would also have resulted in a Clinton victory in 2016.