That only offers Big Sur. I was in fact at the recovery page earlier: here’s what I posted on UseNet (the uk.comp.sys.mac newsgroup):
I obtained the Mojave installer from the AppStore, so that should be OK. I put the installer on an external SSD, but trying to run that under Big Sur just gives the message that it doesn’t run under Big Sur. So I installed Mojave on the external SSD using another Mini. That part worked OK. But when I tried to use that as a startup disk, I soon got into the security hole that startup from an external device was not allowed.
Next thing was that Big Sur got pissy about my password. I could login but the p/w was refused for unlocking any SystemPrefs pane, even though User&Groups said I was an Admin user who could “manage this machine”. I got round this by re-installing Big Sur - over the Internet. Then the p/w was OK again, I could turn off the no-booting-from-external-device security.
I made the SSD into a bootable Mojave installer using instructions I found on MacWorld. That then showed up as a selectable startup device, but on booting it, it then said that “macOS needs reinstalling on this device”.
So far it’s looking as if Apple is locking out any chance to install Mojave instead of Big Sur.
(I have a laptop running Big Sur, I could look to see what the Recovery Page offers there).