Package nbd-tool

Failed to find a solution:

no platform:
2025-05-16 17:25.23 [INFO] Solving for ocaml-base-compiler,
                           nbd-tool, constraints ocaml-base-compiler<=5.3.0,
                           nbd-tool=6.0.0 using opam_repository_commit cf409d95af00ff822422bd76b657ed213b661401

2025-05-16 17:25.25 [INFO] base: eliminated all possibilities in 0.69 s

2025-05-16 17:25.25 [INFO] = base =

2025-05-16 17:25.25 [INFO] Can't find all required versions.
Selected: angstrom.0.16.1 base.v0.17.2 base-bytes.base base-threads.base
          base-unix.base bigstringaf.0.10.0 cmdliner.1.3.0 conf-libssl.4
          conf-linux-libc-dev.0 conf-pkg-config.4 cppo.1.8.0 csexp.1.5.2
          cstruct.6.2.0 cstruct-lwt.6.2.0 dune.3.18.2
          dune-configurator.3.18.2 fmt.0.10.0 io-page.3.0.0 logs.0.8.0
          lwt.5.9.1 lwt_log.1.1.2 lwt_ssl.1.2.0 mirage-block-unix.2.14.2
          mirage-device.2.0.0 num.1.5-1 ocaml.5.5.0 ocaml-config.3
          ocaml-options-vanilla.1 ocaml-syntax-shims.1.0.0
          ocaml_intrinsics_kernel.v0.17.1 ocamlbuild.0.16.1 ocamlfind.1.9.8
          ocplib-endian.1.2 parsexp.v0.17.0 ppx_cstruct.6.2.0
          ppx_sexp_conv.v0.17.0 ppxlib_jane.v0.17.2 rresult.0.7.0
          sexplib.v0.17.0 sexplib0.v0.17.0 ssl.0.7.0 stringext.1.6.0
          topkg.1.0.8 uri.4.4.0 nbd-tool&ocaml-base-compiler ocaml-variants
          ocaml-base-compiler ocaml-base-compiler
- io-page-unix -> (problem)
    No usable implementations:
      io-page-unix.2.3.0: Availability condition not satisfied
      io-page-unix.2.2.0: Availability condition not satisfied
      io-page-unix.2.1.0: Availability condition not satisfied
      io-page-unix.2.0.1: Availability condition not satisfied
      io-page-unix.2.0.0: Availability condition not satisfied
- mirage-block -> mirage-block.2.0.1
    nbd-tool 6.0.0 requires < 3.0.0
- nbd -> nbd.6.0.0
    nbd-unix 6.0.0 requires = 6.0.0
- nbd-tool -> nbd-tool.6.0.0
    User requested = 6.0.0
- nbd-unix -> nbd-unix.6.0.0
    nbd-tool 6.0.0 requires = 6.0.0
- ocaml-base-compiler -> ocaml-base-compiler.5.3.0
    User requested <= 5.3.0
- ocaml-compiler -> (problem)
    ocaml-base-compiler 5.3.0 requires = 5.3.0
    Rejected candidates:
      ocaml-compiler.5.5: Incompatible with restriction: = 5.3.0
      ocaml-compiler.5.4: Incompatible with restriction: = 5.3.0
      ocaml-compiler.5.3.0: Requires ocaml = 5.3.0
      ocaml-compiler.5.3.0~rc1: Incompatible with restriction: = 5.3.0
      ocaml-compiler.5.3.0~beta2: Incompatible with restriction: = 5.3.0
      ...
- ocaml-variants -> (problem)
    Rejected candidates:
      ocaml-variants.5.5.0+trunk: In same conflict class (ocaml-core-compiler) as ocaml-base-compiler
      ocaml-variants.5.4.0+trunk: In same conflict class (ocaml-core-compiler) as ocaml-base-compiler
      ocaml-variants.5.3.1+trunk: In same conflict class (ocaml-core-compiler) as ocaml-base-compiler
      ocaml-variants.5.3.0+options: In same conflict class (ocaml-core-compiler) as ocaml-base-compiler
      ocaml-variants.5.3.0+BER: In same conflict class (ocaml-core-compiler) as ocaml-base-compiler
      ...
- ppxlib -> (problem)
    ppx_cstruct 6.2.0 requires >= 0.16.0
    ppx_sexp_conv v0.17.0 requires >= 0.28.0 & < 0.36.0
    Rejected candidates:
      ppxlib.0.36.0: Incompatible with restriction: >= 0.28.0 & < 0.36.0
      ppxlib.0.35.0: Requires ocaml >= 4.08.0 & < 5.4.0
      ppxlib.0.34.0: Requires ocaml >= 4.04.1 & < 5.4.0
      ppxlib.0.33.0: Requires ocaml >= 4.04.1 & < 5.3.0
      ppxlib.0.32.1: Requires ocaml >= 4.04.1 & < 5.3.0
      ...