If you have a check with the link to NXP homepage, e.g., for i.MX products -
i.MX Applications Processors | Multicore based on 32-bit and 64-bit Arm | NXP Semiconductors
can find various of i.MX family products for different solutions and purposes, and with higher performance than i.MX6ULL.
You can also check the products selector for its status of each product - a link shared by @_angelo_
i.MX6ULL is still alive.
Best regards
Harvey
nxp has a nice per-feature product selector,
https://www.nxp.com/products/product-selector:PRODUCT-SELECTOR?category=c731_c380_c127&page=1
with also "active" flag, please have a look