This is the answer. Don't vote for third party candidates, by that point it's too late.

Vote for candidates in the primaries that are adamant about voting reform/ranked choice voting. Normalize it at state and local levels. Then, it will become a viable option at the national level.

This can happen quickly with the right advocacy and the right candidates, but good candidates are indeed hard to come by.

Speaking of state and local, that is where change is going to happen with ranked choice voting. State and local governments can move much faster than the federal government to institute ranked choice voting. Because states have a high degree of autonomy on holding their own elections, they can prove that ranked choice is a viable option for local, state, and maybe even federal offices.

No, ranked choice has serious issues and won't likely fix the issue. I'd prefer to avoid citing specific alternatives because they all come with their own biases and trade-offs. One example of surprising results is the Burlington, VT mayoral election, which is contentious because the winner was neither the plurality or majority winner.

That said, I think it's a case of "don't let perfect be the enemy of better." If RCV is on the ballot, I'll vote for it. But I'd very much prefer one of the other many alternatives because I think it doesn't resolve the spoiler effect satisfactorily and can have very surprising results.

I highly recommend looking into the various alternatives and reading up on condorcet winners before jumping on the RCV bandwagon.

Regardless I think an even better solution is to focus on fixing gerrymandering. I think we should consider proportional representation in the House, which should get more third parties elected and give us a real shot at breaking the two party system there. I think we'll always have one of the two major parties in the White House just based on voter demographics, but changing at least on house of Congress should force the President to actually work across party lines instead of waiting until their party gets a majority. Having Democrats and Republicans need to cater to the greens, libertarians, etc would be awesome.

You could start with congress members. Or your city council. Prove a 3rd party can win small battles first.

This is truth. The old adage about throwing your vote away isn't exaggeration, or even opinion. In a First Past the Post election, is just math. And math doesn't care about anyone's sense of moral righteousness.

until the Republican party is defunct

Everything is true except this. It's good to have at least two healthy parties competing for voters. So often, single party states allow the dominate party to get lazy because it no longer has to work hard to get votes.

At least ideally, the end result would be an electorate that is further to the left and Republican party that is not as crazy conservative. Overton window shifting and all that.