You won’t be able to set this up on Webflow. You need to get a web server and install it there.
Installing Mautic on Webflow would be like trying to install Wordpress or Drupal on Webflow. It’s a standalone system so it needs it’s own server structure.
Now I imagine there’s ways to make Mautic and Webflow communicate with each other. For example you can probably link forms from Webflow to go into Mautic’s automated system, but again it’s two separate systems communication with each other. Rather than a “plugin” being implemented natively.
It looks like they have a free demo available on their website. https://www.mautic.org/demo/ I suggest you try that out before investing more time in set up and integration.
Let me know how it goes