It’s generally possible using a guide here: Support embedding Discourse in an iframe - #13 by denvergeeks - Feature - Discourse Meta
Unfortunately, with that done there are issues with iframed Discourse functionality – it gives error and it is much less secure (no protection against cross-origin attacks and clickjacking).
<html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title></title> </head> <body> <h1>iframed discourse</h1> <iframe style="width:100%; height:600px" src="https://discourse.intelli-ua.com/"></iframe> </body> </html>