2018 mini: Clean install of macOS

[iAssimilated]

Greetings! My 2018 mini has developed a quirk where it no longer wants to update macOS. It has been suggested I perform a clean install of macOS to see it that clears up the problem (also to help determine if I have a hardware issue before my AppleCare expires in November). The reason for this post is to make sure I have everything straight in my mind for the process. So, here goes:

1. I have purchased a spare external SSD to perform a Time Machine backup.
2. I have downloaded the full installer for Big Sur 11.4 and created a bootable USB.
3. Once in recovery mode I am aware I have to run the Startup Security Utility to allow booting from an external drive.
4. I will run Disk Utility to erase the internal SSD (format as APFS).
5. I will boot the USB and install macOS.
6. Once installed I will have the setup assistant migrate from another Mac or drive (from my Time Machine backup).
7. Wait patiently.
8. Verify I can once again update without issue when the next version of Big Sur is released.

Am I missing anything?

Also, I am aware I cannot do this with my eGPU plugged in, but should I have my other external drives plugged in during the process? My external drives store my iTunes and Steam libraries. Will I have any problems with them disconnected as long as I don't launch those programs?

 

[DeltaMac]

Step 3b. Try the bootable USB to see if you can actually boot to the BigSur installer.
Sometimes (for whatever reason) the bootable doesn't, well, boot, and you need to go back and correctly make that bootable installer.
Of course, you have to boot to the installer before erasing your internal SSD.
(The installer will make the boot partition APFS, so no real reason to do that. I continue to format as Mac OS Extended (journaled) and let the installer do the changeover. It can make you more confident that the install gives a good install. (And probably makes no difference at all, but simply the method that I use )
While you are formatting - format the device, and not just the boot partition. You have to change the View menu to "Show All Devices" before you will see the device.

your steps look OK, and should give you a good result (assuming that you have a good backup before you start!)