The MediaEmbed plugin which is part of Flarum's TextFormatter and that can be enabled via the FoF Formatting or Selective MediaEmbed extensions is the commonly used solution to auto-embed sites like YouTube.
I don't see the site you link in the list of supported websites though https://s9etextformatter.readthedocs.io/Plugins/MediaEmbed/Sites/
If your video hosting website provides a link to a direct video file (not a web player), you might be able to embed the raw video using the AutoVideo plugin or similar (accessible through FoF Formatting as well, and other extensions). This might not work on all browsers and devices since it would only render one video file and will not be able to switch codecs based on the device.
If neither work, but the platform has an official iframe-based embedded player, you could write the MediaEmbed template for that site and load it locally or submit it for inclusion in TextFormatter itself. This will require writing some code.
There are also extensions that allow manually integrating an arbitrary iframe in a Flarum post but I would not recommend enabling such an extension on a forum unless you are certain you understand how it works and that the extension enforces only admins have access to this feature.
