There is a vibration in masculine voices that is often described as "gravelly". It is not something that voice changing software knows how to add or remove. It leads to masculine voices that are too soft (not much gravel in an AFAB voice) and to feminine voices that are robotic (too much gravel in an AMAB voice). There are techniques that you can learn to add or remove those qualities from your own voice. Once you do that, the pitch shift sounds more realistic. So my answer is an amount of vocal training to help you add gravel to your voice. More on reddit.com

This might sound like a weird suggestion, but you could probably check out r/transvoice for some tips More on reddit.com

Folks ar audioengineering might know more

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What I’ve found playing around is that nothing is going to change your voice’s gender entirely electronically, unless it’s like recording your voice and playing it back in an AI synthesized voice or something. When it comes to making my voice more passable when I was early in training, I turned up clips of my voice by 10-40hz in pitch and was impressed by how much of a difference it makes- however that was with me using with a feminized speech pattern; which is very important. No voice changer (save for something that literally re-synthesizes your voice) is going to instantly “make you sound female” without you putting in some effort of your own to change your speech characteristics. This is largely because there are a lot of small aspects that go into a “natural female voice” that no speech modifier can adequately replicate. More on reddit.com