I am working on a project where client has SharePoint 2019 on premises installed and setup. They are using the modern UI. In addition, they have certain HTML built up full page applications and they would like to make their SharePoint 2019 one place stop to access everything. So I am looking for a way to render this web app on a sharepoint page.
I am not really looking to just add a quick link which user can click on and access rather rendering whole web application inside the web part, is it possible to do in SharePoint modern 2019?
If its too much complicated to do in modern UI, I am open to render the web application on a classic page, need guidance here for best practices.
Any help is appreciated, thanks.