I think calling what happened on January 6th a coup attempt is a bit overstating what happened. And even if you want to call it a coup attempt from some of the protesters there, some of whom certainly broke the law to some degree, to then claim that Trump orchestrated or was in charge of a coup attempt seems silly.
Clearly he is a bad loser, and he believes the election was taken from him, I don't think thinking or saying that should be illegal. I also don't think that him gathering supporters for a further political career should be stopped, I see the bigger problem to freedom in the big media houses, particularly Facebook and Twitter, having so much power that they can unilaterally destroy someone's chance to be heard in any meaningful way, these organizations shouldn't have that much power, particularly since they are owned and run by one or a handful of people, it's an immense danger to freedom and democracy.
If Trump were to plan to organize an armed take over of the United States, of course that would have to be dealt with by the states structures as it would be terrorism, treason or insurrection, however I don't see evidence of such a conspiracy. A lot of it also seems to me to be Democrats being just as bad winners as Trump is a bad loser.