I've spent quite some time yesterday trying to figure it out how to get UTM's and add them as a User Custom Field. After some long research and support requests, I discovered it is not possible.
Currently I'm using Elementor Forms, but I was informed by the tec support that even with ConvertKit native form it is not possible.
I would like to request this feature, as it is very powerful to track where the user entered the funnel from and how well it converted. This is not something new, would be great if we could do it.
If there is any sort of way around that, please let me know. Adding UTM's as tags would also work.