I did the top screen shortly after getting the car. Bit of a minefield that one and a ballache. Essentially, its an android powered unit that reads CANBUS info. Not unlike the BMW ones. The difference with this one is that you need to remove a PCB from the original headunit and plug it into this one. It has Carplay built in and goes back to the factory reversing camera/parking sensors when needed so that's all we use it for really but, you can plug in a sim card, use any android app etc. If you're interested in more info then Google "L494 Merryway" and you'll find a few threads on a couple of different forums. I paid around £1000 but it's now available for around half that figure.
You can still fully use the original car system which sits on a layer behind the new one, Ie you press the "HOME" button and the OEM system pops up.
Things have moved on a bit since I got that unit and there are now copies of the facelift infotainment available that work the same as above but have the adjustable tilting screen same as the latest OEM. Only downside is that it takes about 60 seconds to boot up when you start the car. Fitment is tricky and not for the faint-hearted.
This thread has pretty good info about the pro's and cons:
https://www.rangerovers.net/threads/10-25-android-head-unit-for-l494-range-rover-sport.338391/
And here's a link to the unit for sale:
https://www.aliexpress.com/item/32880929708.html
The lower screen is a replacement for your aircon controls, again just like the OEM facelift. This is what I fitted yesterday. It also shows you what drive mode the car is in when you turn the drive-mode knob (albeit a bit laggy). Everything works as per OEM and you can choose between light and dark backgrounds (without auto night/day switching). It also has a SYNC button which means you don't need to go into the heating controls on the main head unit just to sync.
Unlike the upper unit, it pops up after only a few seconds when you switch on the ignition. Fitting isn't too bad either.
I paid around £400 delivered from a seller on AliExpress:
https://www.aliexpress.com/item/1005003610542578.html
The listing is a bit confusing as they sell both systems, but I only purchased the Aircon unit option from them. Also the new, titling upper unit they sell needs a new dashboard trim (as you'll see) but these seem to be all LHD so I'm not sure if they are available in RHD form. My main unit follows the form of the updated tech in the pre-facelift so no new dash trim required other than the glossy black frame that sits around the screen (which came with it.