create usb installer for compatible macs on older mac

Hi friends!

is there a proper method to get the installer from/onto a 2010-macbook air?

The reason is as follows:

I want to upgrade my mac minis (2018 and 2014), which only have flaky lte/4G connection.

At home, connection's very good, but here I have incompatible macs only.

Apple support instructs us how to create a bootable Mac OS 11 installer stick, so I assume this is a legal procedure. Downloading and preparing the usb-stick at home would be far more comfy, but...