first I found:

B' L
D'
F' D B' L2 F2 U//cool DR in 9 but bad corners

then I noticed the 3 move extension has the same arrangement of pieces so:

R2 B' L
D' F' D B' L2 F2 U//2c3 (10)
(D2 B' R2 U2 F' R2 F')
(B2 R2)//19

Final: R2 B' L D' F' D B' L2 F2 U R2 B2 F R2 F R2 U2 B D2

other:

B' L'
D' B2 F D B U' B D//4c3 (10)

B' L
(F U) F' L2 R2 F U//4c3 (9)

F R F' B L'
F2 D2 F U F//4b2 (10)
B2 D2 R2 F2 D R2 D'
L2 D2 B2 L2//solve (21)

Final: F R F' B L' F2 D2 F U F B2 D2 R2 F2 D R2 D' L2 D2 B2 L2

nice linear

other:

(R') R U' L
(U) F2 D2 F U' F2 U//4b2 (11)

(R2 U D B' D)
L2 F2 R U2 F//4b2, this one also has 4ht trigger 4ht 21 but I didn't find it (10)

(U) U' R U
L F' R2 B' U2 F2 R//4b2 (11)

(B) D F2 D F'
(L2 D2 R D)//4b2 (9)
[L' D2 L F2 R U2 D2 L]
F2 U D L2 U D//M slice (21)

[]->R' B2 L D2 R F2 B2 R (21)

Final: D F2 D F' R' B2 L D2 R F2 B2 R F2 U D L2 U R' D2 L2 B'

why does a 4b2 2e need this kind of htr + double slice to get optimal...

other:

L2 F' D B L
D R2 F2 D2 F//4b2 (10)

(D F2 L)
(D2 F' L2 B D)//2c5, would have tried this seriously if the corners weren't in the most doomed position ever