How do I use my existing KeePass database on my new iPad without iTunes on a computer?
The key file has a file extension: .key

I tested the following with Dropbox and an iPad running iOS 11. I deleted my existing key file for the test:


rename your key file with a .key extension
move the newly renamed key file to a shared folder in a cloud (or anything that the iPad can also access)
on your iPad, open the app for the folder share and find the key file
export the key file ...
one of the options should be "Open In..." tap it
you should get a list of apps you can copy the key file to and one of them should be MiniKeePass, tap it
this opens MiniKeePass with the key file listed under "Key Files"


That should work. Again, I did this from Dropbox, so another folder sharing service might behave differently.