iMac 2019 / No sound output device

When you did the factory reinstall did you migrate your user data back to the new installation?

If you did then download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

You’re restoring to factory condition, no bootcamp. Sure, it’s different. Based on your description, your bootcamp is suspect IMO, so it needs to go. You can partition-reinstall it once MacOS works as it’s supposed to. If/when you get there, I would scan it for malware/viruses etc. before using it.

Looks like an hardware issue. I would schedule repair https://getsupport.apple.com/. The estimate is free, however if it’s too expensive, you can get a USB sound card. All the best.

Was the clean reinstall with bootcamp partition intact? I would restore it to factory i.e no bootcamp and see if that fixes it (after backup of important stuff). Good luck.

Your English is excellent😉. You have my inputs, the rest is up to you as you see best. Maybe someone else will reply with better ideas. All the best.

That was fast! Why not schedule service? I don't see any other option. Good luck anyways!

Although in French and I don't read it I didn't see any of the usual suspects. It might be time to make an appointment at the nearest Genius Bar for a free diagnostic check.

👍