What HT processor HDMI 2.1, and does that matter?

ARC is never as good as direct source.  Usually I connect sources directly to the HT Processor.  Then use the HDMI output on the processor to connect to the TV.

The HDMI cable recommendation is based on budget. The older Wire World Starlight 5-2 are a good cable, but they are getting rare and harder to find (probably because I'm always recommending them).  You can find the used on ebay or usaaudiomart sometimes.  I do have a couple of 1M and 2M cables.

If you are willing to get a really expensive cable, the Nordost Heimdall 2 is awsome, but $800 retail. 

Always get 2 meter minimum even if you don't need it.  The 1 meter cables do not perform as well because of digital signal reflections.

For real budget, the cryo-treated Neotech NEHH-4200 from Audio Sensibiliy is typically less than $100 for a 2 meter.

Thank you as always. $100 is about as much as I would want to pay for a cable that is connecting a PS5 or a Fios box to my HT processor. I will be sure to get a 1.5 meter or 2 meter cable instead of a 1 meter. I might try that Neotech cable and just see if it works, but if I did want a cable that was certified HDMI 2.1, do you have any recommendations? 

HDMI 2.1 is so new that there aren't good testing methods for this.  In reality, it is supposed to mean that the cable will support up to 42.6 Gbit per second data bandwidth.  Many manufacturers will "say" that it's HDMI 2.1 certified, but who can tell?

The best I can give you are a couple of cables that are actually tested and certified for HDMI 2.0.  This means that the cable has been tested to support up to 18 GBit per second, which is enough for full bandwidth 4K video.  If you google for "DPL Labs" you will get the company and you can drill down into their site to get the list of certified cables.

Out of that entire list, the only two I would recommend that come close to your budget is a USED Wire World Ultraviolet 7 HDMI or a USED Nordost Blue Heaven HDMI.  It's hard to say which one of these would be better.  The Nordost uses better copper.  However, the Wire World Ultraviolet has bigger 24awg conductors so there will be more "oomph" in the audio and better color saturation, but it could have a noiser digital signal which can come across with video noise or bright audio.

If you look closely, that cro-treated Neotech is almost exactly the same as the Nordost Blue Heaven.  It's just that the Neotech has never been tested for "certification" on the newer hdmi standards.  I bet that these two cables would test almost equal to eachother!