No disk available at ‘select disk where you want to install Mac os’

In Disk Utility, select Show all Devices from the View popup menu.

Do you see a device at the top of the list probably named something like Apple SSD 500GB

Hope you don’t mind me jumping in, I’m having the exact same problem. My daughter gave me her 2017 MacBook Pro w/TB today and when following the instructions to re-install Big Sur, in an attempt to reset it and wipe any data she may have left on there, I also managed to “lose” the 500GB drive (Macintosh HD). I’ve read many threads across various sites but none have given me any ideas on how to get it back. It does not appear in Disk Utility. I’m new to macOS and was hoping to use the MBP to train myself in readiness for a switch from Windows. Not a great start ;-). Any help would be much appreciated.

Run Disk Utility and see if the drive is formatted for a Mac. It needs to be GUID Partition Map and APFS format for Big Sur.

Thanks fro the reply Barney-15E

This morning the missing disk is showing under Internal, as “disk0s2”, where as yesterday all I was seeing in DU was the macOS Base System image.  I cannot mount “disk0s2” as it returns error -119930868, so will pop down to our local Apple support centre.  Thanks again.

That does sound like something failed with the disk.