I have been a Mautic user since the very beginning. I chose Thrive Themes for my WP site because they had a Mautic Integration. But a few years ago Thrive stopped supporting the integration and now it does not work at all.
Judging by the number of posts on this forum on this topic, I am not alone in my frustration. One can use the std Mautic forms and plug them into Thrive, but mucking about with CSS to get them to look ok sucks. Even more so when there are gorgeous out the box Thrive Leads forms to use, plus a powerful reporting dashboard and AB testing functionality inside of Thrive.
After messing about with APIs, Webhooks, and other 3rd party plugins I have finally been able to get a pretty robust Mautic Thrive Integration working. The biggest challenge was to get the Mautic tracking pixel to fire when the lead form is completed so Mautic would associate the correct IP address/browser with the newly identified contact.
Here is how I did it. Hope you find it useful.
Thanks to @joeyk, @steverobinson and @leoschuler for their contributions in helping this non-coder solve this issue. I think this could be used for other form builders, provided they could pass the form info via URL.
PS I have tried to post replies to the more recent threads on this topic, so forgive me if you see my post about this solution dotted around the forum.