The last supported Vivado release of the RXAUI core is version 4.4 (Rev. 6) in Vivado 2019.1.
This core will not be available in future Vivado releases.
The RXAUI core can continue to be used in Vivado 2019.1 or earlier and it might be possible to use the core generated in Vivado 2019.1 in later versions for Vivado.
For future support needs, contact Missing Link Electronics: