How can I transfer photos from my desktop iMac to my iPad, without using iCloud?

You can use iTunes / Finder to transfer photos from the mac to the iPad through USB or Wifi.

See here: Sync photos between your Mac and iPhone or iPad - Apple Support

Or you can use Airdrop: Use AirDrop on your Mac - Apple Support

Yes, the steps above are for transfering photos to the iPad from the Mac. Photos that exist on the Mac can be moved onto the iPad with either of those 2 methods.

The Airdrop option can be used both ways.