The best way to do it is calling the html from .gs file with the following code:
.gs file:
var es = SpreadsheetApp.openById('SPREADSHEET_NAME');
var sheet = es.getSheetByName('SHEET_NAME');
var url = es.getRange("A1").getValue();
const htmlTemplate = HtmlService.createTemplateFromFile('HTML_NAME_FILE');
htmlTemplate.url = url;
const htmlForMail = htmlTemplate.evaluate().getContent();
You might add in your HTML file the following code line:
<html>
<head>
<base target="_top">
</head>
<body>
<a href= <?= url ?> > link </a>
</body>
</html>
You will will see the blue tipic text underlined with a hyperlink inside, like this:
Link
With the diference that this can change depending the value of the cell that you referred before.