User-Approved MDM (UAMDM) was first added in 10.13.4 and any system that was enrolled in an MDM prior to that was automatically made UAMDM. User Approved Kernel Extension Loading (UAKEL) was the only UAMDM required setting at the time. With Catalina, we now have PPPC, UAKEL, and Remote Control requiring UAMDM.
As you need UAMDM for these to work, pushing the configuration profiles through an MDM is the supported and required method. Side loading profiles with BigFix is a temporary solution and will soon disappear, if it even works on the latest macOS (I’m unsure). Rumors are the profiles command will be discontinued soon and that an MDM will be the only way of providing profiles.
I would not count on the profiles command working on future operating systems.
I highly suggest you implement an MDM immediately.
Device Enrollment will allow you to add your serial numbers to an MDM and request that users enroll. A enrollment notification can be shown on users systems with the command:
sudo profiles renew -type enrollment
With some MDM solutions you can make a pkg to enroll systems. This package can be pushed with BigFix, but does not enroll as UAMDM for systems 10.13.4 and newer. Enrolling systems before they upgrade past 10.13.4 is highly suggested.
With both the Device Enrollment request and pkg enrollment, you can prompt users to enroll and do user approval with the UMAD tool:
BigFix does poorly with reporting Profiles status, requiring a task to output the status to update any analysis or relevance. Apple is pushing MDM very hard and it’s going to be the way of managing your systems in any appreciable way moving forward.
I’d suggest Jamf, Moysle, Filewave, micromdm, or a similar solution.