Converting multiple Auth0 tenants to Universal Login with custom domains

Currently we are running about 7 auth0 tenants(one for each dev/prod environment we use). Each tenant has it’s own apis, applications, and Universal Login page. The problem we are running into is Safari is blocking auth0’s cookies being set (show’s as 3rd party) so login will fail. We have implemented a custom domain in one of the tenants to solve the issue. While it works fine, would we then need to elevate every auth0 tenant to allow for a custom domain per tenant or is there a better way? Maybe converting to multi-tenant application? Any help would be greatly appreciated. Thanks.