It's not really a reference design, critical analysis shows it has very narrow application beyond the technology demo, lacking ethernet, much analogue, or SDIO, LSE clock, etc.
The screens here tend to have a very short production lifespan, whilst there may be some deep stock floating around, I'd seriously doubt they can be reordered. If the design is refreshed it will likely migrate to a different screen, with a capacitive touch sensor.
The STMPE811QTR has been dropped due to low up-take, ie not sufficient millions of units, and while it has niche applications these lack sufficient real volume.
https://community.st.com/s/question/0D53W00000UAUTBSA5/hi-there-is-there-any-footprint-and-pin-compatible-part-to-substitute-the-stmpe811qtr-part-i-just-saw-an-obsolesce-noticekind-regardsraul