Original summary:
emergency console: not installed plymouth results in inappropriate error
message obfuscating genuine errors reported by journalctl -xb

Emergency session log ought not be obfuscating genuine errors by reporting
error in an optional service that is purposely not installed. The following is
the final message in the journal after a required filesystem failed to mount:

"Subject: Process /usr/bin/plymouth could not be executed
Defined-By: systemd
Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
The process /usr/bin/plymouth could not be executed and failed.
The error number returned by this process is ERRNO."

Yet, there are, and never were, any plymou* rpms installed.

Observed in TW 20201215.