For XPLL, designs where CLKIN_DESKEW is connected to CLKIN will need to be re-implemented in Vivado 2021.2.1. Alternatively, change the deskew logic to use one of the clock outputs for CLKIN_DESKEW.
Note: Vivado 2021.1.x - Versal Clock Calibrated Deskew Timing issues requires users of the 2021.1.x software versions to apply a patch for a skew issue with the Calibrated Deskew.