Not sure how you enable a sound when you're booting the pc, but I do know how to enable a sound after login.

1. Search for "startup applications" in the launcher and start it up.
2. Add a startup program
3. Name it whatever, i named it login sound
4. In the command section you type the following:
paplay /use/share/sounds/Pop/stereo/notification/system-ready.oga
5. Save
6. Logout of your acc or restart your pc, relog and you'll hear the sound

Maybe [this can help](https://askubuntu.com/questions/1232364/how-to-enable-startup-sound-on-ubuntu-20-04)

The title says it all; How do i enable boot sounds on pop\_os!

Enable boot sound