Does the version of plymouth you're using have add_consoles_from_file() in main.c ? If not, pulling in the commits that add that function and then subsquently fix that function may fix this issue.
We used to infer serial consoles from the kernel command line. These days we read them directly from /sys/class/tty/console/active
Does the version of plymouth you're using have add_consoles_ from_file( ) in main.c ? If not, pulling in the commits that add that function and then subsquently fix that function may fix this issue.
We used to infer serial consoles from the kernel command line. These days we read them directly from /sys/class/ tty/console/ active