When you don't vote, you're really just voting for "whoever happens to win". So I count the non-voters among (R) supporters, or at least as "OK with Trump". Otherwise, they would have voted.

Abstentions can be the most powerful vote, and with great power should come great responsibility. That's often not taught well enough in schools.

Abstentions can seem the laziest vote sometimes, but that doesn't diminish their power nor their responsibility. It is a freedom to be allowed to cast an abstention. Real democracy needs to allow for abstentions, especially explicit abstentions.

(In recent primaries there have been races where I have explicitly cast an abstention. No one will have read my "I don't care who wins this primary, I care who wins the general election" statements, but they are statements to be made. Right now some of the "strategy" in the US two-party system is one-party poisoning the primary vote of the other party by inflaming it with in-fighting in ways that leak into the general election. You have a harder time to win general elections when your candidate is already on fire coming out of the primary. "It doesn't matter who wins, let's stop in-fighting," is a message I can try to write on the ballot, even if not enough people hear it, it feels like the more powerful and responsible vote.)

The goal shouldn't be to get to 100% of people voting in every election, the goal should be to educate people that not voting is tacitly accepting the results of other people's votes. The goal should be teaching people that abstentions are a freedom, a right, a privilege, and should be treated as powerful and treated with responsibility.

I don't think that makes sense. If Harris had happened to win through some minor change in the timeline (she came very close after all), would those people whom you call R supporters instead somehow be D supporters, just because of that minor change in the timeline?

As for "OK with Trump", I think that describes some non-voters. However, there are also non-voters who are more accurately described as "not OK with either side, indeed dislike both sides so equally that neither one seems like the slightly better option".

There is also the factor of swing states. In most of the US, your vote for President pretty much doesn't matter. You almost might as well just put it in the trash. The vote in your state is, barring a massive political shift, locked in for one of the two major candidates. Now, yes, you can still send a message by voting in a non-swing state. But it's understandable why some people would just not bother to vote in a state where the outcome is almost predetermined.