Despite kernel command line
"console=ttyLP0,115200 earlycon=lpuart32,0x5a060000,115200"
on an NXP i.MX 8QM based Variscite VAR-SOM-MX8 module based device, I am not
seeing any kernel serial output other than EFI stub:

Loading Linux 5.19.8-1-default ...
Loading initial ramdisk ...
EFI stub: Booting Linux Kernel...
EFI stub: EFI_RNG_PROTOCOL unavailable
EFI stub: Using DTB from configuration table
EFI stub: Exiting boot services...

or without EFI:

Starting kernel ...


Having ruled out a red herring of
EFI stub: ERROR: Failed to install memreserve config table!
as caused by old U-Boot 2018.03 having a hardcoded config table array size of
2, the lack of output most likely is because of:

CONFIG_SERIAL_FSL_LPUART=m

git-blame points to a SLE15-SP2 sync:
https://github.com/openSUSE/kernel-source/commit/769684a2fa08#diff-a9e1c2425c9e8e93ddd3e6ee09170fbf9ca6182cdfcafde64937d42cfe05a5d5L4287

Serial Kconfig options need to be built-in (=y) in order to enable their
sub-option *_CONSOLE=y, needed for both console= and earlycon= kernel options.