Apple business manager - whitelisting free apps for all users

No. Software, even free software, requires acceptance of a license. ABM provides your organization a centralized way to license applications in volume to avoid the use of Apple IDs on the devices. Follow the procedure you are doing and likely have been doing for decades on the desktop. If a user needs a new app, they request it. Once you approve its value in your workflow, license it in ABM and scope it to devices in Intune.

While unrestricted access to free apps might sound like the right path, it will lead to the installation of a lot of nonsense. If these are institutional devices, managed them as such and keep the garbage and time wasters off the devices.