ATST 3.0 hardware transcoding using NVIDIA GTX 1660 not working

After reading through

When I try hardware transcoding ATSC 3.0 recordings and also live using a web player or iPhone with stream quality 4Mps (force transcoding), it's not working. It's not a big deal because I can always switch to software transcoding and it works. Is it because atsc 3.0 hardware transcoding is still not supported? or just Nvidia hardware not supported..