no 4 k option when sending through sound bar.

Skyworth TV 50" SUD9300F

That 2021 TV has 3 HDMI 2.0 ports, as well as S/PDIF optical out. Google couldn’t find any details on ARC (if present, on which HDMI port?). Seems like a normal feature to specify?!?

I tried to find an online manual, but that doesn’t seem to be publicly available.

Soundbar Samsung HW-R550

That 2019 soundbar has two HDMI ports, one HDMI-in, one HDMI-out, as well as optical. Use of the HDMI port(s) requires turning on CEC (Anynet+ in Samsung speak). The HDMI ports on this model conform to the HDMI 1.4 standard, which does not support 4K with HDCP. Hence no 4K from Apple TV when used for video passthrough.

If your TV has an ARC port, then use that for the connection between the TV and audio system. That is what ARC does: a return channel for audio. Else use optical.

Apple TV →[HDMI]→ TV with audio passthrough setting →[HDMI ARC]→ soundbar or

Apple TV →[HDMI]→ TV with audio passthrough setting →[optical]→ soundbar

You may need to set Apple TV to use Audio Format: Dolby Digital 5.1 (or Stereo); instead of Auto.

You will need to set Apple TV to use Audio Output: TV Speakers to have it output audio over HDMI.

For best advise, we’d have to examine the exact specifications of the equipment in this setup.

Please share the model TV and the model soundbar. Thank you.