scan from Brother printer

See this Apple article: Print wirelessly from your Mac to your printer

https://support.apple.com/en-gb/guide/mac-help/mchl3c1a7aef/mac

I just ran into this issue on my new M1 Max Macbook Pro. For some reason the OS does not seem to be downloading the scanner drivers when it automatically downloads drivers after adding a new printer or scanner. I would try downloading the specific scanner drivers for your printer from the brother website, install them, restart and the scanner should now be showing up in airprint.

Reset the Printing System and re add the printer. When it discovers the printer it may list several Kinds. Try different ones if necessary. If it shows Bonjour select that.