Can I fit a graphics card for HDMI 2.1 in my 2019 Mac Pro?

That model Sony Bravia appears to be a 4K resolution TV set up to 120 Hz refresh rate. That resolution at that refresh rate requires HDMI 2.1, and cables need to have certification and tags for 'Ultra High Speed/48G'.

But if you can get it working that way, it is backward compatible to earlier versions of HDMI.

The graphics card you have now (AMD Radeon Pro Vega II) supports HDMI 2.0 and can provide 4K at 60 Hz. it would need the same certified cables.

You don't need anything beyond that to do what you said you want.

The cable matters adapter is a USB-C adapter, limited by USB-C which has fewer data pathways than ThunderBolt. it can attain 4K at 60 Hz on a Mac (essentially HDMI 2.0) but no faster.

That cable/adapter looks like it will work for 4K at 60 Hz, which is adequate, but you are NOT coming close to the HDMI 2.1 capabilities (or problems) with that adapter. Nor are you spending $1000 on a new card to get an imperceptive increase in refresh rate.

HDMI was invented for High definition TV sets, running at 720-Interlaced. HDMI works fine with any old cable that way. HDMI continues to work at double the data rate for 720-progressive, which has twice the data. HDMI just squeaks by at 1920 by 1080-p.

Above those speeds, it start to heat up and requires a certified cable, labeled "premium high speed".

At HDMI 2.0, the protocol was completely overhauled, the signaling method changed completely, and one data pathway that used to be a cloak is re-purposed as a data lead. 5 volt signaling was retained.

At HDMI 2.1, the speed was cranked way up, but the 5 volt signaling was retained. Switching high-resolution, high refresh rate data at these speeds not only approaches the physical limits of how fast circuits can switch, but at 5 Volts, the signal rivers get really HOT.

So if you choose to convert a signal from some other protocol to HDMI 2.1, the adapters can approach 160 degrees F.

If you must connect using HDMI, and you can possibly go direct HDMI cabling without adapters, that is superior. You withheld the information that you had already dedicated your Only HDMI port for another display.

Your conclusion "adapters are bad" is a shortcut that never came from me.

But I happily own "HDMI is Bad."

<< the end of the HMDI 2.1 cable has a slightly different shaped end >>

HDMI 2.1 requires a CERTIFIED (with certification tag) Ultra High Speed / 48 G cable.

HDMI 2.0 can get by with a certified Premium High Speed cable

HDMI has standard cable-ends.

What kind of cable do you have? take a picture and post the picture, or choose from these standard display connectors:

.

No, that does not get a higher refresh rate, and will still get really hot -- for nothing.

Instead of any adapter or adapter/cable it is better to do DIRECT HDMI cable. That will get you full resolution, just not the 120 Hz refresh rate you get from the Play Station.

You defined what you wanted as HDMI 2.1 4K at 120 Hz. None of the items you mentioned so far will do that from your Mac.

Anything and everything you have mentioned will work at 4K at 60 Hz, supporting HDMI 2.0 without issue. Use what you are familiar with, and at least then it's 'the devil you know'.

That one should also be fine, with four HDMI inputs.

Don't skimp on the HDMI cables. For HDMI 2.1, you will need "Ultra High Speed" /"48G" HDMI cables, those will work for every version of HDMI.

HDMI uses the same plug all the way through. But the capabilities of the various flavors of cable vary wildly, and it is important to use cables appropriate for the highest speeds when you want the highest speeds to work reliably.

If you can plug in your PS2 and get picture on the Bravia, you will have no trouble doing the same with your Mac, using a direct HDMI cable.

HDMI continued to use 5 Volt signaling levels. At the speeds required for HDMI 2.1, adapters from ThunderBolt get so hot, they can burn your skin. USB-C does not have enough bandwidth for the sizes and speeds you are looking for.

Sorry, you said PS 5 and I looked up PS 5, but wrote PS 2. My error.

It's not a question of ThunderBolt-to-HDMI gets a little hot. Adapters to HDMI 2.1 get so HOT most vendors will not MAKE any adapter for HDMI 2.1, because of risk of injury to you and because they burn out quickly.