Today I successfully changed out the screen on my XS Max using a $100 part from iFixit. TrueTone may be broken (thanks, Apple), but my phone is functional again. Now, if only I had an easier way to replace the rear glass panel.
P.S.—Some sources say that a hot plate at 100C for 1-2 minutes is good at loosening up the back. And there are Chinese-origin handheld programmers for transferring TrueTone data to a new screen (if the screen has an embedded EEPROM chip).