I think it seems appropriate to call the variant without the 20(3) cage in N5 A192X V1.5.
It started almost as easily as A192X and for quite a time I was finding it a more enjoyable puzzle. Then my solving path almost ground to a halt and I found myself using a couple of much harder steps to achieve the key breakthrough. HATMAN was right in his choice of which puzzle was the main Assassin and which one the variant.
Here is my walkthrough for A192X V1.5
Prelims
a) 11(3) cage at R1C1 = {128/137/146/236/245}, no 9
b) 22(3) cage at R1C2 = {589/679}
c) 19(3) cage at R1C5 = {289/379/469/478/568}, no 1
d) 22(3) cage at R1C8 = {589/679}
e) 10(3) cage at R1C9 = {127/136/145/235}, no 8,9
f) 22(3) cage at R2C1 = {589/679}
g) 20(3) cage at R2C9 = {389/479/569/578}, no 1,2
h) 10(3) cage at R6C3 = {127/136/145/235}, no 8,9
i) 22(3) cage at R6C7 = {589/679}
j) 11(3) cage at R7C4 = {128/137/146/236/245}, no 9
k) 10(3) cage at R7C5 = {127/136/145/235}, no 8,9
l) 21(3) cage at R7C6 = {489/579/678}, no 1,2,3
1. 45 rule on D/ 3 innies R4C6 + R5C5 + R6C4 = 22 = {589/679}, 9 locked for N5 and D/
2. 45 rule on D\ 3 innies R4C4 + R5C5 + R6C6 = 21 = {489/678} (cannot be {579} which clashes with R4C6 + R5C5 + R6C4), no 1,2,3,5, 8 locked for N5 and D\
2a. 8 of {678} must be in R5C5 (permutations with 6 or 7 in R5C5 clash with R4C6 + R5C5 + R6C4) -> no 6,7 in R5C5
3. 19(3) cage at R1C5 = {379/469/478/568} (cannot be {289} which clashes with R5C5), no 2
4. 45 rule on R5 3 innies R5C456 = 13 = {139/148/238} (only combinations containing 8 or 9 for R5C5), no 5,6,7
5. Hidden killer pair 1,2 in R46C5 and R5C46 for N5, R5C46 contains one of 1,2 -> R46C5 must contain one of 1,2
5a. 10(3) cage at R7C5 = {136/145/235} (cannot be {127} which clashes with R46C5), no 7
6. R46C5 contains one of 1,2 (step 5)
6a. 45 rule on C5 3 innies R456C5 = 16 = {169/178/259/268} (only combinations which contain 1 or 2), no 3,4
7. 3 in N5 only in R5C46, locked for R5
7a. R5C456 (step 4) = {139/238}, no 4
8. 4 in N5 only in R4C4 + R6C6 -> R4C4 + R5C5 + R6C6 (step 2) = {489} (only remaining combination) -> R5C5 = 9, placed for D\, R4C4 + R6C6 = {48}, 4 locked for D\
8a. R4C6 + R5C5 + R6C4 (step 1) = {679} (only remaining combination), 6,7 locked for N5 and D/
8b. 5 in N5 only in R46C5, locked for C5
9. 10(3) cage at R7C5 (step 5a) = {136} (only remaining combination), locked for C5 and N8
9a. Naked triple {478} in 19(3) cage at R1C5, locked for N2
9b. R5C46 = {13} (hidden pair in N5), 1 locked for R5
10. 10(3) cage at R1C9 = {145/235}, 5 locked for N3 and D/
10a. 8 on D/ only in 13(3) cage at R7C3, locked for N8
11. Hidden killer pair 1,2 in 11(3) cage at R1C1 and R1C3 + R3C1 for N1, 11(3) cage contains one of 1,2 -> R1C3 + R3C1 must contain one of 1,2
11a. 4 in N1 only in R1C3 + R3C1 -> R1C3 + R3C1 = {14/24}
11b. 45 rule on N1 2(1+1) outies R3C4 + R4C3 = 2 innies R1C3 + R3C1 + 10
11c. R1C3 + R3C1 = {14/24} = 5,6 -> R3C4 + R4C3 = 15,16 = [69/96/97], no 5,8
12. 3 in N1 only in 11(3) cage at R1C1, locked for D\
12a. 11(3) cage at R1C1 = {137/236}, no 5
12b. 5 on D\ only in 13(3) cage at R7C7, locked for N9
13. 22(3) cage at R1C2 = {589/679}
13a. 6 of {679} must be in R3C4 (R1C2 + R2C3 cannot be {67} which clashes with 11(3) cage at R1C1), no 6 in R1C2 + R2C3
14. 45 rule on N7 2 innies R7C1 + R9C3 = 2(1+1) outies R6C3 + R7C4 + 11
14a. Min R6C3 + R7C4 = 3 -> min R7C1 + R9C3 = 14, no 1,2,3,4
14b. Max R7C1 + R9C3 = 16 -> max R6C3 + R7C4 = 5, no 5,6,7,8, no 4 in R6C3
15. 11(3) cage at R7C4 = {146/236/245} (cannot be {137} because R7C4 only contains 2,4), no 7
16. Hidden killer pair 1,2 in 13(3) cage at R7C7 and R7C9 + R9C7 for N9, 13(3) cage contains one of 1,2 -> R7C9 + R9C7 must contain one of 1,2
16a. 3 in N9 only in R7C9 + R9C7 -> R7C9 + R9C7 = {13/23}
16b. 45 rule on N9 2(1+1) outies R6C7 + R7C6 = 2 innies R7C9 + R9C7 + 11
16c. R7C9 + R9C7 = {13/23} = 4,5 -> R6C7 + R7C6 = 15,16, no 4,5
17. 13(3) cage at R7C7 = {157/256}
17a. 22(3) cage at R6C7 = {679} (only remaining combination), CPE no 6,7 in R7C7
17b. 9 of 22(3) cage must be in R7C8 + R8C9 (R7C8 + R8C9 cannot be {67} which clashes with 13(3) cage), 9 locked for N9, no 9 in R6C7
17c. Naked pair {67} in R6C47, locked for R6
17d. Killer pair 6,7 in 22(3) cage at R6C7 and 13(3) cage at R7C7, locked for N9
17e. Min R6C7 + R7C6 = 15 (step 16c) -> no 7 in R7C7
18. Naked pair {48} in R8C7 + R9C8, locked for 21(3) cage at R7C6
-> R7C6 = 9
19. R8C9 = 9 (hidden single in N9)
19a. R9C3 = 9 (hidden single in R9)
19b. Naked pair {67} in R4C36, locked for R4
20. 22(3) cage at R2C1 = {679} (cannot be {589} because R4C3 only contains 6,7), no 5,8, 9 locked for N1, CPE no 6,7 in R3C3
21. 5,8 in N1 only in 22(3) cage at R1C2 = {589} (only remaining combination) -> R1C2 + R2C3 = {58}, R3C4 = 9
21a. R2C1 = 9 (hidden single in N1)
22. 22(3) cage at R1C8 = {589/679} -> R1C8 = 9
22a. 7,8 only in R2C7 -> R2C7 = {78}
23. R4C7 = 9 (hidden single in C7)
23a. 20(3) cage at R2C9 = {389/479}, no 6
23b. Killer pair 3,4 in 10(3) cage at R1C9 and 20(3) cage at R2C9, locked for N3
23c. Killer pair 7,8 in R2C7 and 20(3) cage at R2C9), locked for N3
23d. R6C2 = 9 (hidden single in R6)
24. R7C3 = 8 (hidden single in R7), R2C3 = 5, R1C2 = 8
25. 4 in R7 only in R7C24, CPE no 4 in R8C3 + R9C2
25a. 11(3) cage at R7C4 (step 15) = {146/236/245}
25b. 2 of {236} must be in R7C4, 5 of {245} must be in R9C2 -> no 2 in R9C2
26. 7 in C3 only in R45C3, locked for N4
26a. 16(3) cage at R5C1 = {268/457}
26b. 8 of {268} must be in R5C1 -> no 2,6 in R5C1
26c. 7 of {457} must be in R5C3 -> no 4 in R5C3
27. R1C3 = 4 (hidden single in C3), R1C5 = 7
28. 11(3) cage at R1C1 (step 12a) = {137/236}
28a. 7 of {137} must be in R2C2 -> no 1 in R2C2
28b. 7 in N1 only in R23C3, locked for C2
29. 10(3) cage at R6C3 = {127/136/145/235}
29a. 1 of {127/136/145} must be in R6C3 (R7C2 + R8C1 = {16/17} => R8C2 + R9C1 = {23} and cannot place 4 in N7) -> no 1 in R7C2 + R8C1
29b. 2 of {235} cannot be in R6C3, here’s how
R6C3 = 2 => R7C2 + R8C1 = {35} => R8C2 + R9C1 = {14} => only even numbers available for 11(3) cage at R7C4
-> no 2 in R6C3
30. 10(3) cage at R6C3 cannot be {127}, here’s how
10(3) cage = {127} => R7C2 = 2, R8C2 + R9C1 = {14}, R8C3 + R9C2 = {36} => R7C4 = 2 clashes with R7C2
30a. -> 10(3) cage at R6C3 = {136/145/235}, no 7
31. R7C1 = 7 (hidden single in N7), R7C8 = 6, R6C7 = 7, R6C4 = 6, R4C6 = 7, R4C3 = 6, R3C2 = 7, R2C7 = 8, R3C6 = 5 (step 22), R8C7 = 4, R9C8 = 8, R23C5 = [48]
32. R1C9 = 5, R2C9 = 7, R3C8 = 4 (hidden singles in N3)
33. 10(3) cage at R1C9 (step 10) = {235} (only remaining combination), 2,3 locked for N3 and D/ -> R8C2 = 1, R9C1 = 4
34. R7C7 = 5, R8C8 = 7 (hidden singles on D\), R9C6 = 2, R9C9 = 1, placed for D\
35. R5C3 = 7 (hidden single in C3), R5C12 = [54] (step 26a)
and the rest is naked singles without using the diagonals.