If you have no preferred pronouns, just say (none) or something
This will help make people feel more comfortable in this comm and has a side effect of showing you support trans people when making comments in other communities. It will also make reactionaries seethe and make it easier for mods to purge them, and make trans people feel safer all over the fediverse.
One way or another, Lemmy has many communities. Even if you don't have any preconceptions about women, others will. And even if it's all in my head and nobody on lemmy has such prejudices -- she/her isn't my identity, but my username is. jsomae is how I choose to present to the world, and I don't want femininity to be a part of how I present.
then to ask simply, how do you want people to refer to you when talking to you online? whether you include a pronoun tag or not, people are going to refer to you
Exactly the same way I expect people to know I'm Canadian. That is to say, I expect people to call me she/her if they recognise me or in the rare event my sex is relevant and surfaces ("my experience as a woman is...").
Pragmatically, most people will he/him me if they are Neanderthalpilled and they/them me if they are based, as is the rule online. :P (and those he/himmers will assume I'm American as well.)