Anti-Knight (AN), also no 4-7 at Knight spacing, although that’s not required to solve this puzzle.
1a. 45 rule on R123 2 outies R45C1 = 4 = {13}, locked for C1, NR4C1 and 16(4) cage at R3C1
1b. R45C1 = 4 -> R3C12 = 12 = {48/57}, no 2,6,9
1c. Naked pair {13} in R45C1 -> no 1,3 in R45C3 (AN)
2a. 45 rule on NR4C1 using R45C1 =4, 2 remaining innies R45C2 = 16 = {79}, locked for C2, NR4C1 and 36(6) cage at R4C2, clean-up: no 5 in R3C1 (step 1b)
2b. 36(6) cage must contain 8 in R45C34, locked for NR4C3
2c. 9 in C1 only in R12C1, locked for NR1C1 and 36(6) cage at R1C1
3. 45 rule on R12 2 innies R2C89 = 12 = {39/48/57}, no 1,2,6
4a. 45 rule on C89 4 outies R1237C7 = 11 = {1235}, locked for C7
4b. 45 rule on C789 3 outies R689C6 = 3 = {123}, locked for C6
4c. 45 rule on NR7C7 2 outies R9C67 = 6 = [24]
4d. R9C67 = 6 -> R8C67 = 11 = [38]
4e. R6C6 = 1
AN eliminations:
R6C6 = 1 -> no 1 in R4C5 + R5C8 + R7C48 + R8C5
R8C6 = 3 -> no 3 in R6C5 + R79C4
R8C7 = 8 -> no 8 in R6C8 + R79C5
R9C6 = 2 -> no 2 in R7C7 + R8C48
R9C7 = 4 -> no 4 in R7C8 + R8C9
Naked triple {679} in R456C7 -> no 6,7,9 in R5C59
[I’ll leave those 4-7 eliminations for now, since SudokuSolver only scores this puzzle at 0.9.]
5a. 15(3) cage at R8C8 = {456} (only remaining combination, cannot be {159} which clashes with R7C7) -> R8C8 = 4, R9C89 = {56}, locked for R9 and NR7C7, clean-up: no 8 in R2C9 (step 3)
5b. R7C7 = 1
5c. R9C1 = 8, clean-up: no 4 in R3C2 (step 1b)
5d. 9 in R9 only in R9C345, locked for NR6C5
5e. 8 in NR6C5 only in 16(3) cage at R6C5 = {358} -> R7C5 = 3
5f. R8C5 = 6 (hidden single in NR6C5)
5g. R9C2 = 3 (hidden single in R9)
AN eliminations:
R7C5 = 3 -> no 3 in R5C4
R8C5 = 6 -> no 6 in R6C4 + R7C3
R8C8 = 4 -> no 4 in R6C9
Naked pair {58} in R6C5 + R7C6 -> no 5 in R4C6 + R68C4
Naked triple {235} in R123C7 -> no 2,5 in R2C5, no 3,5 in R2C9, clean-up: no 7,9 in R2C8 (step 3)
6. R4C4 = 3 (hidden single in NR4C3), R45C1 = [13]
6a. 36(6) cage at R4C2 = {345789} (only remaining combination) -> R4C3 + R5C34 = {458}, locked for NR3C4
6b. R5C5 = 2
6c. 2 in R4 only in R4C89, locked for NR1C9
6d. Naked triple {679} in R5C267, locked for R5, 6 also locked for NR4C3
6e. Naked triple {458} in R5C348, locked for R5, 4 also locked for NR4C3
6f. R5C9 = 1
6g. 4 in C5 only in R1234C5, locked for NR1C3
AN eliminations:
R4C4 = 3 -> no 3 in R2C3
R5C5 = 2 -> no 2 in R37C4 + R6C3
R5C9 = 1 -> no 1 in R3C7
6 in R5 only in R5C67 -> no 6 in R3C6
6 in C7 only in R45C7 -> no 6 in R4C9
Naked triple 4,5,8 in R4C3 + R5C34 -> no 4,5,8 in R7C3
7. Naked triple {279} in R7C389, locked for R7
7a. R3C3 = 3 (hidden single in NR1C1)
7b. R1C7 = 3 (hidden single in NR1C3)
7c. Naked pair {25} in R23C7, locked for NR1C8, clean-up: no 7 in R2C9 (step 3)
AN eliminations:
Naked pair {25} in R23C7 -> no 5 in R3C5, no 2,5 in R3C9
8. 45 rule on R12 3 outies R3C789 = 14 = {248} (cannot be {257} because 2,5 only in R3C7) = [284], R2C789 = [539], R5C8 = 5, R9C89 = [65], R6C78 = [97]
8a. R147C8 = [129], R146C9 = [683], R4C3 = 5
8b. Naked pair {67} in R5C67, locked for R5 -> R45C2 = [79], R45C7 = [67], R5C6 = 6
8c. R3C12 = [75], R3C456 = [619], R4C56 = [94], R2C6 = 7, R9C5 = 7
8d. R1C34 = [72] (hidden pair in NR1C3)
8e. Naked triple {458} in R1C56 + R2C5, locked for 27(6) cage at R1C4 -> R2C4 = 1, R9C34 = [19], R8C4 = 7, R78C3 = [29], R8C12 = [51]
8f. R7C3 + R8C23 + R9C2 = [2193] = 15 -> R7C2 = 6 (cage sum)
AN eliminations:
R4C6 = 4 -> no 4 in R2C5 + R5C4
and the rest is naked singles.