Hello, @Alex_mjl
Thanks for the question.
Yes, it could be used in UART mode, the kernel could be compiled as listed in the BSP UM, but one important limitation is that LLCE LINFlexD can be used as a serial console once the LLCE mailbox driver has been loaded, typically after reaching the Linux console.
However, by default, the serial driver is loaded before loading the LLCE modules, so that only LINFlexD consoles are enabled during the boot. You may have to make some modification to the system to insure the driver loading order to have the LLCELIN correctly probed by the driver.
Best Regards
Chenyin