You can use two separate VPNs if you use a work profile to run the second one. I’m not sure if this would work for your use case though. Check out Shelter if you want to give it a try.

I set up a notify group for each of us. I use notify.me and add/remove the devices as needed.

notify:
- name: me
  platform: group
  services:
   # - service: mobile_app_pixel_2_xl
    - service: mobile_app_pixel_6

- name: her
  platform: group
  services:
    - service: mobile_app_iphone

Then you can use it like any other service:

service: notify.me
data:
  message: Test
  title: Alert!

It’s probably a bit late for a new ESP32, but if not I’m a fan of the M5Stack Atom Lite. It’s a solid little device and comes in its own case.

The Home Assistant team publishes the analytics they collect (for those that allow it). The integrations and add-ons pages might interest you if you haven’t seen them.