I am attempting to copy some site collections over from a SharePoint 2016 installation to a new SharePoint 2019 installation, however when I take a file generated by Backup-SPSite and I attempt to Restore-SPSite on the 2019 version it completes successfully but no data is created? I have read that the change in versions may be an issue but there is no error to say that. Is this possible, if not what is the best way to move a site collection from a SharePoint 2016 instance to a SharePoint 2019 instance? Thanks!
The "nominal" way of migrating to a higher version is fully documented by MSFT: https://learn.microsoft.com/en-us/sharepoint/upgrade-and-update/upgrade-to-sharepoint-server-2019. I would recommend following it since this is the only way to ensure you have a fully supported system.
I have used the trick you mention in the comment [for dev purposes ONLY] to move between different patch levels of 2016: http://sadomovalex.blogspot.com/2013/11/how-to-restore-site-collection-from.html. This is NOT recommend for production systems...