If what you're looking for is a decentralized pseudonymous system. Then this is absolutely possible with today's cryptography.
It's called public-private keys. You create a private key that you can use to "sign" your messages. And people can verify that is was you that wrote the message by using the public key.
No one can pretend to be you because only you have access to your private key and the public key can't be used to find out what the private key is.
It's still anonymous because you don't have to say who you are when you create the private key.
It's not perfect because the same person can create as many different keys as they want. So you can't really "ban" someone. They'll just create a new key and pretend to be someone new.
If you're in a swing state. You vote for Biden.
If you're not in a swing state, you vote third party.
Don't not vote, by voting you make your intention and commitment very clear. Even if your third party candidate never has a chance, mainstream politicians may notice the interest in that third party candidates platform and adopt some of his/her policies.
Participate in your state's primary elections. There's a lot more diversity of policies there and you can make your voice heard there as well.
Participate in your city and state elections, the amount of money effort and attention placed on federal elections (especially presidential) is completely outsized compared to local elections. Which means the amount of influence that you can have as an individual relative to amount of power the offices that you have influence over is huge compared to the same calculation at the federal level.
Many politicians start at the state and municipal level. So your influence there can be very helpful. Also if Trumps gets some success at creating a authoritarian dystopia at the federal level, it can be mitigated at the state and municipal level. Just like how each state can make sure to protect the right of abortion despite the supreme court flip on the subject.