I tried to identify which are wall cells and which are cage cells. Identifying cage cells often identifies wall cells and vice versa. I started on the largest and smallest cages.
E.g., 17/2 cage in n12.
Since n12C6 and n12C8 must be wall cells, implies the cage is n12C9 and either n13C7 or n22C3.
Either way -> n23C1 must be a wall cell.
Since neither n13C7 or n22C3 can be an 8 -> n12C9 = 8 and one of n13C7 and n22C3 = 9.
Using the diagonals, many of the 8s in the puzzle may be placed.
Another e.g., 10/4 n23 must be {1234} and it cannot include the given 2 in n23.
-> Must use the 2 in a different nonet.
Since n24C7 and n33C3 must be wall cells -> cage must be n23C789 (= {134}) + one of n22C9 or n33C1 (= 2)
-> n23C456 and n32C3 must be wall cells
Another e.g., 6/2 in n34 must be cells 1,2 or cells 1,4 in n34.
-> n34C5 is a wall cell.
Another technique I used...
42/8 in n44 can only use at most cells 6,8,9 in n43, and cells 6,8,9 in n34.
-> cannot use 8 in either n34 or n43
-> must use 8 in n44.
Since 42/8 cannot use cells 1, 2, 4 in n44, and 8 can only be in cells 1, 2, 4, or 5 in n44
-> n44C5 = 8 and the 42/8 cage must use it.
-> n44C24 are wall cells.
Trying to work out where the cage cells for the 42/8 and the 35/5 must go while still leaving connected wall cells leaves very restricted choices for where those cages can go.
Final technique,
Since cells 1,3,4,5,6 in n23 are all wall cells, n23C2 must be a cage cell.
Only cage that can reach it is 45/9 cage from n24 going through n14 and n13.
-> n13C8 must be a cage cell.
-> 17/2 cage must be n12C9 and n22C3 = [89]
