Formatting Mac mini M4 SSD from recovery without losing macOS reinstall option

As you state, you're not booted into Recovery. When you are, you will be able to erase what is shown in your example screenshot as Volumi di Macintosh HD. Doing so will enable you to reinstall macOS and preserve the ability to boot into Recovery.

You cannot format the startup volume (the OS will not allow it), and notice how Container disk1 and disk2 do not even show up in DU? Those are the Recovery OS, and macOS doesn't show them because it does not want you to erase them.

it’s already been alluded to, there is no reason to ever erase the system short of needing to revert to a previous macOS version. Go into the general system settings reset options and use erase all content in settings.

MacOS is mounted as a Reid only volume from a Krypto graphically sealed snapshot. It can never be modified except for updates from Apple erasing it and reinstalling will achieve nothing except a waste of time.

Erase your Mac and reset it to factory settings - Apple Support

I have seen a few posts where that process resulted in requiring a DFU reset,. I don’t know if there are any other issues with those attempts, but erasing the entire drive is certainly a higher probability of resulting in the need for a DFU reset

You do not need to use Recovery to restore. Just use the erase all content feature under general, transfer or reset then select erase all content. You could go to recovery, erase the drive then reinstall the OS but that is not as easy. Erasing the drive will not prevent you from installing the OS. I have done that through recovery and it works fine.

You should erase/reformat Macintosh HD, which is the usual startup disk for the Mac (unless you're renamed it, as I have). The Recovery OS is on a separate partition, you would not be able to format that anyway.