Domain mapping additional domains on a single MU site

Hi, I have stopped using the Domain Mapping plugin as it is no longer supported and we had issues with one of our website when we tried to switch the Primary Main Domain to be the live one. I read that this plugin is no longer supported so I changed the domain manually (in Edit Sites).

The problem is that some of my clients have additional domains that point at the same site and I would rather still keep the original url on the system (such as runyourownwebsite.uk/site1 etc..) . Is there a recommended plugin or another way to do this please?

Thank you very much

Clive