I listed the URLs you can sync subscription-manager from here:
How do i register Oracle Linux version 7 without subscription-manager - Support - TheForeman
I also listed some packages that should probably be filtered out since Oracle packages things in such a way that their packages obsolete subscription manager (this was a huge pain in Oracle Linux 7 and I just kept doing it for Oracle Linux 8). I do not have a URL yet for Oracle Linux 9, but hopefully the individuals that package subscription-manager into these repositories take pity on us and do so for EL9.