Corrected your list.
UCL Squad of 21 can consist of maximum 21 Association Players + 0 HNG, 20 Assoc + 1 NHG, 19 + 2, 18 + 3 etc down to 4 +17 NHG. 17 is the maximum NHG players allowed.
Club Trained (1)
Austin
Association Trained (6) (maximum 21)
Spence, Davies, Gray, Maddison, Johnson, Solanke
NHG (23 CL) (maximum 17)
Vicario, Kinsky
Porro, Udogie, Romero, VDV, Danso, Dragusin, Vuskovic, Takai
Bissouma, Bentancur, Sarr, Kulusevski, Bergvall
Kudus, Yang, Gil, Solomon, Odobert, Tel
Son, Richarlison
List B - Lankshear, Devine and Scarlett and most of the Academy players.
Current squad is 6 HG and 23 NHG =29.
Maximum allowed is 21.
So at least 8 players need to be chopped from NHG list.
Or potentially 7 NHG and Davies.
I can't see any other of the association players being left out.