Plenty of options in the app "Learn" sections - endgames, drills, also lessons like checkmate in 3. Can't say it's helped me, though, probably should learn more and play less...
Mate Practice Drills

There's literally android apps called matein1, matein2, and matein3.. you can download for this specific purpose. :)

One thing not to do, is search for ‘matein3’, because apparently Apple wants to offer threesome hookup apps and AI girlfriends.
Every game I play, I run through the Game Review and it always points out the many ways I ‘could’ have won, but didn’t see it. Win or lose, it invariably lets me know I had a checkmate at some point, even if it is way off (mate in 12, pffft). It is worse when I win but wasted half the game shuffling pieces into the perfect ladder check after eating up every opponent piece.