Continuing working through my backlog, the next variant I tried was A107 V2 which I found that I hadn't started.
Thanks Mike for a challenging variant!
My solving path is very similar to Afmob's and we used the same breakthrough move but our reasoning for steps was sometimes different so I'm posting my walkthrough.
Here is my walkthrough for A107 V2.
Prelims
a) R4C12 = {14/23}
b) R4C34 = {59/68}
c) R4C67 = {16/25/34}, no 7,8,9
d) R4C89 = {39/48/57}, no 1,2,6
e) R5C12 = {15/24}
f) R5C34 = {19/28/37/46}, no 5
g) R5C67 = {29/38/47/56}, no 1
h) R5C89 = {39/48/57}, no 1,2,6
i) R6C12 = {29/38/47/56}, no 1
j) R6C34 = {69/78}
k) R6C67 = {13}
l) R6C89 = {16/25/34}, no 7,8,9
m) 19(3) cage in N1 = {289/379/469/478/568}, no 1
n) 8(3) cage at R1C3 = {125/134}
o) 21(3) cage at R4C5 = {489/579/678}, no 1,2,3
p) 10(3) cage at R8C3 = {127/136/145/235}, no 8,9
Steps resulting from Prelims
1a. Naked pair {13} in R6C67, locked for R6, clean-up: no 8 in R6C12, no 4,6 on R6C89
1b. Naked pair {25} in R6C89, locked for R6 and N6, clean-up: no 2,5 in R4C6, no 7 in R4C89, no 6,9 in R5C6, no 7 in R5C89, no 6,9 in R6C12
1c. Naked pair {47} in R6C12, locked for R6 and N4, clean-up: no 1 in R4C12, no 2 in R5C12, no 3,6 in R5C4, no 8 in R6C34
1d. Naked pair {23} in R4C12, locked for R4 and N4, clean-up: no 4 in R4C67, no 9 in R4C89, no 7,8 in R5C4
1e. Naked pair {16} in R4C67, locked for R4, clean-up: no 8 in R4C34
1f. Naked pair {15} in R5C12, locked for R5 and N4 -> R4C34 = [95], R6C34 = [69], R5C3 = 8, R5C4 = 2, R6C5 = 8, clean-up: no 3 in R5C6, no 3,6,9 in R5C7, no 4 in R5C89
1g. Naked pair {48} in R4C89, locked for R4 and N6 -> R4C5 = 7, R5C67 = [47], R5C5 = 6, R4C67 = [16], R6C67 = [31]
What an incredible start to an Assassin variant! The hard work will come later.
2. 45 rule on R12 2 innies R2C19 = 11 = {29/38/47/56}, no 1
3. 45 rule on R89 2 innies R8C19 = 9 = {18/27/36/45}, no 9
4. 45 rule on N1 1 innie R3C3 = 1 outie R1C4 + 1, no 1,3,7 in R3C3
4a. 45 rule on N1 3 innies R123C3 = 9 = {135/234}, 3 locked for C3, N1 and 8(3) cage at R1C3, no 3 in R1C4, clean-up: no 8 in R2C9 (step 2), no 4 in R3C3
4b. R3C3 = {25} -> no 2,5 in R12C3
4c. 8(3) cage at R1C3 = {134}, CPE no 4 in R1C12
5. 45 rule on N3 3 innies R123C7 = 12 = {345} (only remaining combination), locked for C7 and N3, clean-up: no 6,7,8 in R2C1 (step 2)
5a. 45 rule on N3 1 outie R1C6 = 1 innie R3C7 + 4, no 2,5,6 in R1C6
6. Naked triple {289} in R789C7, locked for N9, clean-up: no 1,7 in R8C1 (step 3)
6a. 45 rule on N9 1 innie R7C7 = 1 outie R9C6 + 2, no 2 in R7C7, no 2,5,8,9 in R9C6
7. 45 rule on N7 1 innie R7C3 = 1 outie R9C4 + 3, no 1,2,5 in R7C3, no 3,6,7 in R9C4
7a. R7C3 + R9C4 = [41/74], CPE no 4 in R7C45 + R89C3 + R9C12
8. 45 rule on N7 3 innies R789C3 = 13 = {157/247}, 7 locked for N7
8a. 10(3) cage at R8C3 = {127/145}, CPE no 1 in R9C12
9. Naked pair {14} in R19C4, locked for C4
10. 17(3) cage in N7 = {269/359/368} (cannot be {458} which clashes with R789C3), no 1,4
11. 17(3) cage in N1 = {179/269/278/467} (cannot be {458} which clashes with R123C3), no 5, clean-up: no 6 in R2C9 (step 2)
11a. 4 of {467} must be in R2C1 -> no 4 in R3C12
12. 3,4,5 in R3 only in 22(5) cage at R3C3 = {13459/23458}, no 6,7
12a. 1 of {13459} must be in R3C5 -> no 9 in R3C5
13. Hidden killer pair 6,7 in R2C4 and R78C4 for C4, R78C4 cannot be {67} which clashes with R9C6 -> R2C4 = {67}, R78C4 must contain one of 6,7
13a. Killer pair 6,7 in R78C4 and R9C6, locked for N8
14. 6 in N2 only in R2C46, locked for R2
14a. 20(4) cage = {1568/2369/2468/2567/3467} (cannot be {1469} which clashes with R1C4)
14b. 6,7,8 of {1568/2567} must be in R2C46 -> no 5 in R2C6
15. 19(3) cage in N1 = {289/469/478/568}
15a. 7 of {478} must be in R1C1 (R12C2 cannot be [74] which clashes with R6C2) -> no 7 in R12C2
16. 15(3) cage in N7 = {159/168/249/348} (cannot be {258/456} which clash with R789C3)
16a. 5 of {159} must be in R8C1 -> no 5 in R7C12
17. 13(3) cage at R7C8 = {157/346}
17a. 45 rule on R7 4 innies R7C1289 = 19 = {1279/1369/1378/1459/1468/1567} (cannot be {2467/3457} which clash with R7C3, cannot be {2359/2458} because {35/45} in R7C89 aren’t consistent with combinations for 13(3) cage at R7C8, cannot be {2368} because no {258} combination in 15(3) cage in N7), 1 locked for R7
17b. No combination for R7C1289 contains both of 3,4 -> R7C89 cannot be {34} -> no 6 in R8C9, clean-up: no 3 in R8C1 (step 3)
18. Hidden killer pair 1,4 in 24(4) cage and R9C4 for N8, R9C4 = {14} -> 24(4) cage must contain one of 1,4 -> {1689/3489/4569/4578} (only combinations containing one of 1,4), no 2
18a. 2 in N8 only in R7C56, locked for R7
19. 20(4) cage in N2 (step 14a) = {2369/2468/2567/3467} (cannot be {1568} which clashes with 22(5) cage at R3C3 which must have 1 or 8 in R3C456), no 1
20. 45 rule on N2 5 innies R1C46 + R3C456 = 25 = {12589/13489/13579/14578} (from combinations for 20(4) cage, step 19)
20a. R1C46 + R3C456 cannot be {12589} which clashes with R3C3
R1C46 + R3C456 cannot be {13579} = [17]+[359] which clashes with 22(5) cage at R3C3 because {13459} must have 5 in R3C3)
-> R1C46 + R3C456 = {13489/14578}, 4,8 locked for N2
21. 20(4) cage in N2 (step 19) = {2369/2567}, 2 locked for N2
21a. 5 of {2567} must be in R2C5 (R2C456 cannot be {267} which clashes with R2C19), no 5 in R1C5
21b. R1C4 + R3C5 = {14} (hidden pair in N2)
22. Hidden grouped X-Wing for 1 in 8(3) cage at R1C3 and 16(3) cage at R1C8 for R12, 8(3) cage at R1C3 contains 1 -> 16(3) cage at R1C8 must contain 1 = {169/178}, no 2, 1 locked for N3
23. 45 rule on R3 4 innies R3C1289 = 23 = {1679/2678}
23a. 1 of {1679} only in R3C12, R3C12 cannot be {19} (because no 7 in R2C1) -> no 9 in R3C12
24. 2 in R7 only in 26(5) cage at R7C3 = {23489/23579/24569/24578} (cannot be {23678} which clashes with 24(4) cage in N8 or 24(4) cage + R9C6 in the case of the {4578} combination)
[Alternatively {23678} can be eliminated by looking at the permutations for 5 innies R7C456 + R9C69 in N8.]
25. R7C1289 (step 17a) = {1369/1378/1468/1567} (cannot be {1459} which clashes with 26(5) cage)
25a. 4,6 of {1468} must be in R7C89 (R7C12 cannot contain both of 4,8 because no 3 in R8C1), no 4 in R7C12
25b. 15(3) cage in N7 (step 16) = {159/168/348} (cannot be {249} because 2,4 only in R8C1), no 2, clean-up: no 7 in R8C9 (step 3)
25c. 9 of {159} must be in R7C1 (R78C1 cannot be [15] which clashes with R5C1) -> no 9 in R7C2
26. 15(3) cage in N7 (step 25b) = {159/168/348}
26a. Cannot be {348}
R8C1 = 4 => R7C12 = {38} => R7C89 (step 25) = {17} clashes with R7C3
26b. 15(3) cage = {159/168}, no 3,4, clean-up: no 5 in R8C9 (step 3)
27. R7C3 = 4 (hidden single in N7), R9C4 = 1 (step 7), R1C4 = 4, R3C5 = 1, R3C3 = 5 (step 4), clean-up: no 9 in R3C89 (step 23)
28. Naked quad {2678} in R3C1289, locked for R3 -> R3C46 = [39], R3C7 = 4, R1C6 = 8 (step 5a), R12C5 = [25], R78C6 = [25]
29. Naked pair {67} in R2C46, locked for R2, clean-up: no 4 in R2C1 (step 2)
29a. Naked pair {29} in R2C19, locked for R2
30. R2C2 = 4 (hidden single in N1), R6C12 = [47]
30a. R2C2 = 4 -> R1C12 = 15 = {69}, locked for R1 and N1, R2C1 = 2, R2C9 = 9, R3C12 = [78], R4C12 = [32], R5C89 = [93]
31. Naked pair {17} in R1C89, locked for R1 and N3 -> R2C8 = 8, R4C89 = [48]
32. R8C19 = 9 (step 3) = [81], R1C89 = [17]
33. R8C9 = 1 -> R7C89 = 12 = [75]
34. R7C4 = 8 (hidden single in C4), R7C7 = 9, R9C6 = 7 (step 6a)
and the rest is naked singles.