I'll link to two mastodon posts that contain a lot lot of informarion and links to various sites that try to be a guidance on trans general and sprcially DIY HRT things.

This one is specifically for testosterone based HRT

https://social.voidkvlt.eu/@void/statuses/01KVQT5V5BKA4RWKYJ9290D3Z2

This is generall knowledge and a bit more focused on estrogen based HRT, which tbf a lot of diy online sources are. DIYHRT is kind of a thing mostly done with estrogen because testosterone is a controlled substamce but yeah, not the point of this post :D

https://queer.group/@dee@treehouse.systems/112417068947512520

Edit: If anyone wants to talk more about DIYHRT feel free to send me a DM :)