How to rebuild mail sending from form_submitted_hook?

Hi, I try to update my website to d10. I have custom module that sends email on form submission and on form_submitted_hook I have a call to \Drupal::service('plugin.manager.mail')->mail().
How can I rebuild it to use symfony_mailer?

I've built simple EmailBuilder plugin and I now what to put in a "build" section, but I am totally clueless how I build other sections, so it will work exactly like old version.

Any tips? I got stuck