Solved! PC to TV with optical to AV - only stereo, no 5.1

Jan 2, 2019
I upgraded my tv to a 4k Samsung NU7100, unfortunately, my receiver (harman kardon 1600 i think) only supports 1080p. I ended up doing PC->TV with HDMI for video and TV optical out->receiver for sound, however, there is only stereo sound, no 5.1

The digital output audio option on the TV is set to PCM and I can't choose Dolby or Dolby+

Are there any solutions other than buying a new receiver?