I had last OS Big Sur in my mac mini from 2014. But programs start crashing, so reason: reinstall OS. I erased all data on disk with utility. CMND R, booting from internet. Utility OS X now have (in white dialog windows) option for Reinstall OS X - but it is El Captain. Always... How to boot from internet and install new OS Bigsur?
Mac mini, macOS 11.0
Try booting into Internet Recovery Mode using Command + Option + R. Unfortunately some Macs tend to default to the oldest version of macOS compatible with the Mac.
Do you have access to another 2014+ Mac so you can create a macOS 11.1 Big Sur USB installer?
https://support.apple.com/en-us/HT201372
Once you boot the installer make sure to erase the whole physical SSD before installing macOS. Even if you did this before I recommend you do it again. This Apple article shows how to reveal the physical drive in Disk Utility:
https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac
If you cannot boot the Big Sur online installer and you don't have access to another Mac compatible with Big Sur, then you will need to first reinstall El Capitan and attempt the upgrade to Big Sur again. I highly recommend creating a Big Sur USB installer this time.
Try booting into Internet Recovery Mode using Command + Option + R. Unfortunately some Macs tend to default to the oldest version of macOS compatible with the Mac.
Do you have access to another 2014+ Mac so you can create a macOS 11.1 Big Sur USB installer?
https://support.apple.com/en-us/HT201372
Once you boot the installer make sure to erase the whole physical SSD before installing macOS. Even if you did this before I recommend you do it again. This Apple article shows how to reveal the physical drive in Disk Utility:
https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac
If you cannot boot the Big Sur online installer and you don't have access to another Mac compatible with Big Sur, then you will need to first reinstall El Capitan and attempt the upgrade to Big Sur again. I highly recommend creating a Big Sur USB installer this time.
How install new Bigsur OS when bootin from Internet?
