The drm-next-kmod port can be enabled for amdgpu (for AMD GPUs starting with
the HD7000 series / Tahiti) or i915kms (for Intel APUs starting with HD3000 /
Sandy Bridge) through kld_list in /etc/rc.conf. radeonkms for older AMD GPUs
can be loaded and there are some positive reports if EFI boot is NOT enabled
(similar to amdgpu).

For amdgpu: kld_list="amdgpu"
For Intel: kld_list="/boot/modules/i915kms.ko"
For radeonkms: kld_list="/boot/modules/radeonkms.ko"

Please ensure that all users requiring graphics are members of the
"video" group.

Older generations are supported by the legacy kms modules (radeonkms / 
i915kms) in base or by installing graphics/drm-legacy-kmod.