It too think that's the case: it's a French drain. (Diagram from Wikipedia).
There are rocks on top of the pipe, and if they are exposed it should be treated as an immovable obstruction (same as cart path), but if the sod on top is consistent with the rest of the area, even though it is in a depression, it should be treated as the general area, unless explicitly mentioned as GUR and/or in a local rule. This is what @Rulesman also stated, above, per the R&A.
You probably flip and hit the shots fat for the most part. Taller less tight turf lets you get away with more poor contact. So, just improve at that - generally building a better swing with better contact, more deformation, more shaft lean, less flipping…
Day 7 (10/24/21) - Practiced chipping today: about 9 balls with my Orange Whip Wedge, followed by about 15 balls with my 58* wedge trying for the same feeling. I got this drill from a Bryan Pate video.