For openSUSE Leap 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:smarty12:ocaml/openSUSE_Leap_15.6/home:smarty12:ocaml.repo
zypper refresh
zypper install ocaml-bigarray-compat
For openSUSE Leap 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:smarty12:ocaml/openSUSE_Leap_15.4/home:smarty12:ocaml.repo
zypper refresh
zypper install ocaml-bigarray-compat
For openSUSE Leap 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:smarty12:ocaml/openSUSE_Leap_15.3/home:smarty12:ocaml.repo
zypper refresh
zypper install ocaml-bigarray-compat