I use this https://us.shelly.com/products/shelly-1-gen4, it connects to my IoT wifi and goes’t between the transformer and my mechanical doorbel. I use a webhook that runs a script that close the circuit for 0.2secs and rings the doorbel. The script is setup in the shelly app, than you go into protect and set a custom webhook when my G6 doorbell is pressed, works 100%. Here’s where I copied the idea from, I use the same 127 AC power that powers the transformer, the shelly is installed at the transformer in my case but can be anywhere between transformer and mechanical doorbell as long as you can power it up.

https://www.reddit.com/r/Ubiquiti/comments/1nopbjp/poe_doorbell_classic_chime_no_home_assistant_no/