Mac mini 2018 Disk Utility stuck at loading disks

See if the problem still happens in safe mode.  Safe mode will often correct weird software behavior by forcing the OS to clear caches, do disk repair and other self-maintenance and housekeeping and temporarily disables third-party mods.

How to use safe mode on your Mac - Apple Support 

You can exit safe mode by restarting your Mac normally, then reevaluate the problem.

If you continue to have trouble, shut down the Mac and disconnect any external drives. Reboot and reconnect your drive(s) one at a time. It may be that a particular drive is having trouble.

Try using different cables.

Reboot your Mac.

Please see: Writing an effective Apple Support Communities question - Apple Community

I concur with D.I. Johnson.

Last few times I had "Loading disks" in Disk Utility, it turned out to be a failing or failed external drive.