Experimental non-binary HRT

(Rough draft, please help by expanding it and adding references!)

Hormone replacement therapy (HRT) is usually presented as a binary, MTF or FTM, and non-binary people seeking hormonal transition are warned of the all-or-nothing effects of sex hormones. But with a little creativity, it may be possible to tailor a hormone regimen towards the changes you want while preserving others. This is almost totally uncharted territory! Most of the info I have on tamoxifen, for instance, is a handful of rumors from bodybuilders using it to prevent gynecomastia while on 'roids, and from a couple trans people who wanted to keep a flat chest.

Anti-Androgens Alone
If you identify as agender or genderqueer (AMAB), or you want to stick to the reversible stuff, you may not want the "feminizing" effects of estrogen but still want to wash out testosterone. Many people elect to take only anti-androgens such as Spironolactone and Finasteride, without adding Estrogen or Progesterone into the mix. However, having some amount of a sex hormone (either estrogen or androgen) is necessary to maintain bone health in the long term. In this case, you could consider a SERM like Tamoxifen to protect from some of the actions of Estrogen.

Hormones

 * Tamoxifen is a selective estrogen receptor modulator (SERM). In some tissues such as the brain it activates estrogen receptors, which may help reduce dysphoria. In breast tissue it antagonizes estrogen receptors, preventing the formation of breast tissue if desired.
 * Tamoxifen may also be taken alongside 17β-estradiol, more research is needed. In this combination, estradiol should still have its effects (combating dysphoria in the brain, redistribution of body fat, smoother skin etc.) while tamoxifen prevents the growth of breast tissue.