lsb-invalid-mta binary package in Ubuntu Focal amd64

 The Linux Standard Base (http://www.linuxbase.org/) is a standard
 core system that third-party applications written for Linux can
 depend upon.
 .
 This package contains nothing else than a fake /usr/sbin/sendmail
 command to fulfill the LSB's requirement of providing this command without
 requiring an MTA to get installed, which once introduces a daemon which
 can cause security problems and second, users get asked questions about
 how they want their MTA configured when in reality they simply wanted to
 install a desktop application or a printer driver, but the dependency on
 LSB compliance pulls in an MTA with the installation.
 .
 The LSB requirement on /usr/sbin/sendmail comes from old times where Linux
 and Unix machines had all fixed IPs and did server tasks in data centers.
 Today's typical desktop Linux machines do not do local e-mail any more as
 users use external e-mail services.
 .
 The /usr/sbin/sendmail always exits with exit status -1 (255) and sends a
 warning message to stderr, so that if a program actually tries to send e-mail
 via the sendmail command the user gets note.

Source package