Links don't work in HTML viewer
For simple .html files that have been uploaded to the Files tab in a channel, after one clicks on the .html file and opens it in the Teams HTML viewer, clicking on links in the HTML page turns the HTML page white instead of taking one to the link's intended destination. This happens when using the "Open in SharePoint" option too. One is forced to always download the file and open it in a browser directly from the local file system. This is very inconvenient.