Hi @Anthony R ,
You have to build SharePoint Framework extensions instead of JSlink. Within the "modern" UI of SharePoint Server 2019 most of those customizations are no longer available. SharePoint Framework extensions enable you to provide similar functionality in the "modern" UI.
1.Create a new SharePoint Framework solution
2.Define the new Field Customizer with JavaScript
3.Test the solution in debug mode
4.Define the new Field Customizer with TypeScript
5.Package and host the solution
6.Bundle, package and deploy the solution
7.Install and run the solution
For Reference: Migrating from JSLink to SharePoint Framework extensions
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.