The one marked eArc should connect to whatever sound system you may have (if anything other than those 2 HP speakers)... be that a Receiver hooked to surround sound "dumb" speakers or perhaps a Soundbar-based setup.
Otherwise plug AppleTV, cable box and PS3 into any of the ports. If you want to keep using only HPs as audio for all of that stuff, I think AppleTV would have to be plugged into the port marked eARC (but am not 100% sure of that, as I don't own HPs and would not opt to use them in that way if I did own some).
Since you have only one more 2.1 port, if you stream any ATMOS movies or shows to AppleTV or Cable box, connect them to your 2.1 ports.
Else, if you have a Receiver-based setup, everything should connect to the Receiver with
ONE cable from Receiver to HDMI 2.1 input and one cable from HDMI 2.1 eARC (output) back to Receiver (which would only get used when watching something using the TV's built-in tuner itself... or something perhaps temporarily attached to TV HDMI ports) because the Receiver will strip off any audio flowing into it to play on the attached speakers.
I'll guess you are leaning on them HPs for TV audio. I suggest moving them to other rooms and using them for what they are best at-
wireless MUSIC- and perhaps setting yourself up with a good Surround Sound system via either a good Receiver & wired speakers or a Soundbar and wireless "smart" speakers. Our ears- even late 70-year-old ears- will easily be able to hear the difference between only stereo sound up front vs. left-center-right up front and at least 2 left & right surrounds behind.
If you do this, eArc out to the subwoofer or Receiver and plug the other stuff into the remaining ports on TV (if you go the soundbar route) or all into Receiver (and only 1 cable from Receiver to TV).
If you want to keep it all fairly simple (like perhaps the goal with those HPs), consider what is called the
Sonos Ultimate Immersive setup... which is their best soundbar for front left-center-right and their best surrounds (300s) for theater surround sound, plus a subwoofer for deep bass. Besides being on (unusual) sale through Fathers Day, these play very nicely with
Apple Music and
many others,
Airplay 2 and have Apple
Home compatibility (which, among other things, gets Siri through Apple devices), etc. For example, if I command my Mac to play a favorite playlist on my Sonos speakers, it "just works."
If you don't think you need the deeper bass but want real surround, their
Premium Surround Set version sans sub is about $600 less during this sale. And you can mix & match with Sonos, meaning you could start with as little as only Arc (soundbar) and add other pieces later to build out a full surround sound setup.
If you go with either option, I suggest buying stands for the 300s if needed on Amazon or similar, where you will pay much less than the OEM ones... unless you perhaps opt to put those rears on maybe existing shelving or similar behind your main seating area.
If you need financing, Best Buy is matching these prices and offering "same as cash" terms.
New TV will bring great new video for your eyes. Consider a big sound upgrade too. Those HPs will do a great job as intended in another room(s).
