There's a relative newcomer to the field of apps that can create bootable installer drives:
"Mist":
Fixed insecure HTTP URLs for certain Firmware files Thanks F1248! Fixed a bug where downloads were not being cancelled when the Escape key was being pressed Thanks F1248! Rolled back the Bootable D...
github.com
(download the ".dmg" file)
Mist will both download the installer AND create a bootable USB flashdrive in one integrated app.
For the latest OS's, I'd suggest using a 32gb flashdrive, formatted to HFS+.
Free and worth a try if you're having continuing difficulties using other means...
EDIT:
I just tried using Mist to download/create a bootable flashdrive.
I picked Monterey (last version).
It took a little time, but went off without a hitch.
The installer boots my 2018 Mini.