It seems to still be a problem with the upstream repositories. We have the same issue from Satellite 6.15 on RHEL8 and Satellite 6.16 on RHEL9. The following URLs all return 404 (Not Found):
https://artifacts.elastic.co/packages/8.x/yum
https://artifacts.elastic.co/packages/oss-8.x/yum
https://artifacts.elastic.co/packages/8.x/apt
Testing the URLs with cURL gives the same 404 error code.