The drop reality
Tridents drop only from drowned holding tridents — a small fraction of drowned spawn holding one, and the drop chance is low even then. The practical route is a drowned farm over water with a Looting III trident-or-fallback weapon loop; expect a project, not an afternoon. You cannot craft a trident — that is what makes it a trophy weapon.
Loyalty vs Riptide — pick one
Loyalty III returns the trident after every throw (the thrower’s weapon), pairing with Channeling for lightning strikes during storms. Riptide III launches you with the throw — mobility magic in rain or water, but mutually exclusive with Loyalty and Channeling. Impaling V boosts aquatic damage; Unbreaking III + Mending keep it alive.
Trident lifestyle
Riptide owners basically fly through rain; Loyalty owners get a returning spear for hunting. Both work beautifully with an ice-road or ocean lifestyle. If your world is mostly desert, weigh that before committing enchant books.