Package conf-dkml-cross-toolchain

Failed to find a solution:

no platform:
2023-08-31 00:02.53 [INFO] Solving for ocaml-base-compiler, ocaml,
                           conf-dkml-cross-toolchain using opam_repository_commit 7dbbdf38edcb4e6e73461f0e7bb2ada6c9314c2f

2023-08-31 00:02.54 [INFO] base: eliminated all possibilities in 0.66 s

2023-08-31 00:02.54 [INFO] = base =

2023-08-31 00:02.54 [INFO] Can't find all required versions.
Selected: base-bigarray.base base-domains.base base-nnp.base
          base-threads.base base-unix.base ocaml-options-vanilla.1
          ocaml-base-compiler&ocaml&conf-dkml-cross-toolchain ocaml
          base-domains ocaml-base-compiler ocaml-system
- conf-dkml-cross-toolchain -> conf-dkml-cross-toolchain.4.12.1
    User requested = 4.12.1
- ocaml -> (problem)
    User requested <= 5.0.0
    conf-dkml-cross-toolchain 4.12.1 requires = 4.12.1
    ocaml-base-compiler 5.1.0~rc2 requires = 5.1.0
    Rejected candidates:
      ocaml.5.0.0: Incompatible with restriction: = 4.12.1
      ocaml.4.14.2: Incompatible with restriction: = 4.12.1
      ocaml.4.14.1: Incompatible with restriction: = 4.12.1
      ocaml.4.14.0: Incompatible with restriction: = 4.12.1
      ocaml.4.13.2: Incompatible with restriction: = 4.12.1
      ...
- ocaml-base-compiler -> ocaml-base-compiler.5.1.0~rc2
    User requested >= 4.04.1
- ocaml-system -> (problem)
    No usable implementations:
      ocaml-system.5.0.0: Availability condition not satisfied
      ocaml-system.4.14.1: Availability condition not satisfied
      ocaml-system.4.14.0: Availability condition not satisfied
      ocaml-system.4.13.1: Availability condition not satisfied
      ocaml-system.4.13.0: Availability condition not satisfied
      ...