It can be problematic.
To my mind, it's a question of specificity. You are attempting to locate a specified location which, by
definition, is a specific or definite
named location. "Nearest entrance to an extra-dimensional space" is not specifically named. "Gate of the Seven Worlds" is a specifically named location. Likewise, "the exit of the maze spell" is specifically named, as is "the labyrinth's exit".
Now the hard part. It denies the finding to an named object or creature at essentially an unnamed locale. So a portable hole and rope trick, being objects, cannot be 'found,' nor could their entrance.
Some would argue by saying "the entrance to Mialee's Rope Trick" makes it a named location. 'Entrance' is a location, but "Mialee's Rope Trick" is not a location. "The exit to the labyrinth", OTH, is a location in a location so it can be 'found.' Further, the labyrinth is a named location, relatively, since you are in it. Yet, "the entrance to the nearest labyrinth" is a location to an unnamed location so it cannot be found. Finally, you could 'find' the "exit of Mialee's Rope Trick" since you are in the location of Mialee's Rope trick attempting to find a location ('exit').
So, essentially, if everything mentioned is a specifically named location, relatively, it can be 'found.'
I'm not a morning person, so hopefully I've explained it decently.