I've been running a multisite in WP and now struggling to get a 2nd domain running. I am not looking to have 1.example.com and example.com or example.com/ex I have 2 separate names, example.com and website.com. Is this possible in WordPress? Or should I detach the Multisite and run 2 whole separate wordpress installations from the same machine?
As @Rup points out in a comment, this is possible in WordPress, natively since version 4.5.
From the documentation:
WordPress multisite subsites may be mapped to a non-network top-level domain. This means a site created as subsite1.networkdomain.com, can be mapped to show as domain.com. This also works for subdirectory sites, so networkdomain.com/subsite1 can also appear at domain.com. Before setting up domain mapping, make sure your network has been correctly set up, and subsites can be created without issues.
Note: You'll need to make sure your DNS servers point to the right place, etc. WordPress doesn't manage DNS for you.