/etc/rc.local is an obsolete script kept for compatibility purposes on systemV systems. I just discovered in Bullseye, the rc.local script is not activated. I knew the systemV support was slowly fading but this came as a surprise. What was supposed to be a five-minute job turned into a three-hour exercise.
I had reason to upgrade a Raspberry Pi operating system (O/S) on a Raspberry Pi 3B to the current version. The O/S for this Pi hardware and its rc.local were operational for a few years. A poorly performing SD card motivated me to upgrade. The old O/S used rc.local to start a number of python scripts. After getting the most current O/S installed on the new SD Card I ported the Pi user directory and modified the /etc/rc.local to start the scripts on reboot. I discovered that nothing happened.
Migrating legacy systems to the current version introduces some new twists. I managed to find some notes on systemctl and port the script startup to the service. I had done some work with systemctl was first introduced. I had to lookup most of the syntax. The online notes failed to work, of course, but with a little perseverance, I created the necessary scripts and contents to have the scripts running as services on systemd.
When companies advertise in their job postings, system administrators needed with 5-10 years of experience which is understandable. I really would like to forget my VAX knowledge to make room for something more relevant:) The longer systems are around the greater need for the old knowledge. A system Twenty-seven years old was the oldest system I replaced. Imagine the changes over twenty-seven years. It was a UNIX database of sorts.