systemic problems require systemic solutions, currently the systemic incentives are for single-party. If you want multiparty you're going to have to want a good deal of constitutional changes or internal party structure changes (although we already have a good amount of that in the form of house caucuses).
Maybe they do though the most powerful movements are grassroots. If it can get enough momentum to outpace the demonization that surely follows growth.
For example, who wouldn't support anti-fascism? That morphed into "antifa" which became the source of all the worlds ills according to the orange goblin. Yet only a fascist could be afraid of anti-fascism.
We "just" need all states to agree, simultaneously, that first-past-the-post elections are dumb, and implement something else (ranked choice, approval, whatever). That would allow other political parties to form and start gaining seats everywhere from local offices up to Congress.
Eliminating the electoral college would of course require amending the constitution, and of course GOP-led states will never be in favor of that, since they benefit from it, and most of the time have not / will not win the popular vote.