> You could have bought a bell...

Over engineering is about the solution, not the requirement:

> I wanted something that lets me play a custom bell

"You could have bought a bell.."

No because similar commercial products were either out of stock or not compatible with my AC voltage.

If you find one that meets your requirements that is an option.

Granted maybe your requirements are ridiculous. But I also had cases where I DIYed a solution because the commercially available solutions all either didn't fulfil the requirements and/or had anti-features that ruled out their use. I haven't had any regret so far with these solutions, with some of these being active for over a decade.

There may be over engineering, but replacing a bought solution that needs to connect to the internet and someone else's computer to ring a bell with a simple 433MHz sender and a MP4-player module isn't that. Do you know what is required for a device to even connect to a WiFi? That alone is more complex than the whole system the user built here.