Not sure what issues you are having with JAMF, I've used many MDM's over the years and JAMF is one of the good one's.
By your message I take it you did a trial and it's expired so you've lost access?
I would raise a support ticket with JAMF and they should be able to sort out access again.
When you enrolled the devices in Jamf did you set the MDM to removable or not? If the MDM profile was set to be removable, you can easily remove the Jamf framework and then if the devices are in Apple School/Business Manager point the devices to your new MDM and then enroll them in there. If the profile wasn't set as removable it will be much more difficult to accomplish the task. Is your Jamf Pro instance on-premise or a cloud instance and what MDM are you switching to @rsmithson?