IMO: with trans people sexuality is more complicated and we're still at a point where our societal and linguistic understanding is lagging behind reality

Yes. It is possible for someone to still identify with a community they were once a part of, even if they are no longer perceived as part of that community.
Your past is a part of you. It doesn't seem "screwy" for someone who once participated in a certain culture (for you, lesbian or WLW culture) to still feel attached to it.

People can grow up religious and later stop believing, but still feel connected to aspects of religious communities. People can spend years of their lives as trained athletes playing sports, and later work a desk job, never even going to the gym anymore, but still relate to a community of athletes.

Parts of your personal narrative are allowed to change as you grow, and you can still identify with the parts of you that are no longer visible to other people!

You are not alone in this, I promise. I am a cis-lesbian in a relationship with a transman (transitioned 12 years ago) and my partner and I experience this same disconnect between identity, community, and perceived community. To most, we appear like a straight couple (even despite my butch presentation). We don't relate to straight people though. We never have. We also don't relate to trans-couples who identify as straight.
We are most comfortable in lesbian or queer spaces, and although my partner sometimes questions whether or not he 'belongs' there, we have yet to experience hostility from fellow lesbians and transmen.

Outside of queer spaces, the world sees us as straight, and because of that we acknowledge that we benefit from "passing-privilege." However, this also causes people to make a lot of inaccurate assumptions about us and our relationship. Neither of us would consider ourselves straight. He is non-op and we consider our sex to be pretty damn gay. We find ourselves having to come out to people over and over again.

Medical intervention(transition), labels, and communities exist to help people survive- to help people connect with others and cope with a society that is obsessed with reinforcing hetero-normativity and perpetuating patriarchal, misogynistic beliefs. No one is obligated to fit perfectly into any one narrative to be able to relate to it and participate in the community.

Where it does matter is in political activism. Acknowledge how the world perceives you (even if that doesn't align with how you see yourself) before you try to speak on behalf of a marginalized community. Let the people who most accurately represent the community be the public voice. If you want to help because you sympathize and relate and understand, give people a platform. Help the voice of the community be heard. Use whatever advantages you may have to make a difference instead. For example, for you, that could be using your gay male presentation to talk to other men/gay men about misogyny or lesbian erasure or anything else that you may understand better than them because it has been part of your lived experience.

And if you aren't keen on activism, there's no rule that says you have to participate. Just don't publicly criticize marginalized voices, because you 'personally' disagree with it. Political activism isn't about individual feelings. If it's not your cup of tea, just stay out and I doubt people will find you problematic.

So long as you can acknowledge where the shared experiences begin and end, you will find people will welcome you in almost any community.

Sexuality is based on sex, not gender, so it makes sense that you would still feel attached to the lesbian label. lesbian just means "female homosexual" and has nothing to do with gender identity. historically, trans men and passing women have always been part of the lesbian community.

I heard people (ok, men) directly say they are 'male lesbians' in the context of supporting feminism. I find the concept silly - at best, dishonest at worst.

People that transition later in life don't usually give up those communities - the communities ostracize or shun them. Confirmation bias demands that communities are self affirming and transition pretty much calls that into question (across the board).

So, my position is that as humans we are not confined by our biology and that includes the inherent sexual preferences.

Step away from what others or society deems appropriate or acceptable. Find what you are comfortable with in your own skin (seems you have at least partially), then BE that. If someone asks, tell them as YOU understand yourself, not in the context or terms of a 'standardized version'. If someone says 'I'm still confused!', then laugh and say "how do you think I FELT, until I just accepted me for who I am" which is a challenge to them to do the same. Good people will accept that, and you. Who cares about the rest?

Sounds like you are basically happy - it's a nice place to be. Don't overthink it!

Go with whatever rocks your boat. Otherwise one is just living a lie, and for the benefit of who?