I'm not sure if this is intended behavior or if there's some technical aspect I'm missing, but as far as I can tell there's no way to use the output of /locate besides running it as a player and clicking on the output in chat. Running it as a function or via a command block doesn't produce a usable chat output even if the function technically executes without error.

EDIT: I have found one limited way to use it:

1. function
   scoreboard objectives add d2 dummy
   execute store result score @a d2 run locate biome jungle
   tellraw @a ["Distance: ",{"score":{"name":"@a","objective":"d2"}}]

This outputs the distance to a set locate target but there's no way to get the coordinates.