I'm the Democrat you probably are referring to. Quite frankly nothing is wrong with your interest in a third party or even having an interest in alternative voting method (Ranked Choice or Star voting) to get a more preferable candidate.
My only thing to bring up is to understand the objective as well as its difficulties. On a federal aspect 'but Trump' is a very real issue. Nobody should be ignorant to harm that having Republicans in the White house & 1 and/or 2 branches of congress is very dangerous & detrimental.
The enthusiasm that people have for wanting to have something better is commendable & shouldn't be discounted. The task to win an executive office is based on electoral college not a popular vote. President Obama & Biden has soon how even that large of an office can be well checked & handcuff to a unaccommodating congress so you need to have more one office to present an alternative. That is fifty sates & with several states having various methods of how they allocate those votes. A third party & Independent candidate run that hasn't spent at least multiple years & decades should really owe potential voters a serious analysis than supposed moral platitudes(There are real harms for Republicans winning). They need concrete real & achievable measurable goals & strategies so their voters can gauge their success a long the way so voters could make rational choices come time for the general election. Democrats & Republicans benefit from a long history of being established players(or the only ones), it can seem unfair but don't be discouraged.
First, read up on your state statues & laws on what it takes to form or be a recognized political party. Then check out some of those recognized especially ones you believe align closest to you. Make sure you aren't reinventing the wheel. You might find out the those parties have platforms you for the most part agree with. Check out those parties state rules & bylaws on how they are governed or operate. If their is possibility to get involved that might be an easier option. There is something meritorious in a state having their own voice or say in a different candidate even if they aren't the presidential pick. Just see how Bernie Sanders's status is viewed as a Independent who caucuses with Democrats. Even as Democrats we got to keep an almost free pickup with Joe Manchin in MAGA country West Virginia & also John Tester in Montana. Distinctions can be made while existing under the umbrella.
There are lots of other avenues to explore that doesn't have to be a national campaign or even a state-wide one. Apathetic voters that don't or rarely do as well as plenty of disgruntled two party members exist to provide a strong base for third parties. Nobody would be upset with third parties increasing the voter pool & providing them with a voice better aligned to their views or interest.
Don't discount the importance of city, county, and state legislators importance in everyone's life. Some states don't prevent minimum wage increases passed at the city level & one insane aspect of RW SCOTUS is municipalities can enact environmental laws they are trying to strip from the federal government. Cities give "incentive" deals to businesses and I've seen them get involved in housing schemes. There are possibilities for improvement. Just Imagine taking that kind of victory separate from Dems or Repubs to the national stage. Also, how much better an individual would feel being involved in that kind of improvement.
(The only challenge would be that both parties at state & federal election filing may challenge petitions to be recognized and later to field candidates with challenges. Easily addressed by CHECKING your state laws. Some states like Florida & Tennessee the party can field their own candidates so check the laws. Be prepared and really try to work on a process to get candidates to support the issues & actions condoned by the group recruiting them. After building a good strong base its really just working on the party's appeal & protect their image from attacks by the Big Two. Establish an ethics committee or other aspect to help guard against accusations. Be accountability & trust in the party but not naive. Not being so paralyzed you have to be afraid but vigilant enough to challenge entryist that are only there to sabotage.)
