You’re not wrong, anything older than a Pi 4 is a bit flawed as an accurate time server. Even the Pi 4 needs a stable temperature or its clock speed will be uns

You’re not wrong, anything older than a Pi 4 is a bit flawed as an accurate time server. Even the Pi 4 needs a stable temperature or its clock speed will be unstable, as there’s no temperature adjusted clocksource, it just uses cpu. On older Pi versions USB is run in kernel instead of on chip, causing thousands of cpu interrupts per second. Also its on board ethernet is run through USB.