If you do decide to try monotherapy, gel is unlikely to give you blood e levels high enough to suppress testosterone production if it's applied as directed (upper arms and thighs) https://transfemscience.org/articles/high-dose-transdermal-e2/ You can get higher levels by applying it to your scrotum, but it's quite irritating https://transfemscience.org/articles/genital-e2-application/

If you want testosterone suppression without an AA, E injections are generally the best option. Vanna pharma is based in the uk and is reputable (not sure if I can post a link here, but the url is on diyhrt.cafe). Her product has a lower viscosity than Lena's so you can get away with 29g fixed needles (higher gauge = thinner needle = less pain). You might need 27g or even luer syringes with a low gauge needle for drawing and a higher gauge for injecting if you order injectable e from elsewhere.

Here's the 27g needles I used to use with Lena's EV https://www.exchangesupplies.org/shopdisp_unisharp_fixed_1ml_green_27.php
Drawing the product from the vial can blunten the tip a little, so occasionally an injection would be a little difficult and painful. It could also take several minutes in winter to draw 0.18ml into the syringe due to the higher viscosity.

Here's the 29g I use with Vanna's EV https://www.exchangesupplies.org/shopdisp_Unisharp_fixed_1ml_yellow_29.php
These are thinner and I'm yet to have a painful injection. It takes around 15 seconds to draw 0.18ml at current temperatures (5-15C).

There are several different esters of estradiol available for injection https://transfemscience.org/articles/injectable-e2-meta-analysis/ , but the most common one is estradiol valerate which is often dosed at 0.18ml of 40mg/ml solution (0.18 x 40 = total dose of 7.2mg) every 5 days. Ideally you'd get a blood test after a couple of months so that you can check your levels and adjust your dosage accordingly.

✅ prefer not to say

If you have a homelab or vps you could try rolling your own with https://hub.docker.com/r/onerahmet/openai-whisper-asr-webservice for the transcription and a foss Tasker alternative for retreiving the voicemail when your dialler app posts a voicemail notification. If you don't have the capability to selfhost whisper, you'd probably have to sacrifice the illusion of privacy (your mobile carrier will always have access to any calls made over their network) and use a transcription service from google/microsoft/openai.

Asterisk https://www.asterisk.org/ might be worth a look too (i.e. selfhost your voicemails)

This is going to blow your mind, but some people are women and some people are gay. Wild.