Am I able to just buy any hot water urn even if it doesn’t have Shabbos mode and use that on Shabbos? what are these Shabbos modes adding besides for shutting off the electric panel? does it stop the water from boiling for the rest of Shabbos, and non-Shabbos mode one would boil throughout Shabbos? would it be a problem to buy a regular basic hot water urn with a spigot without any Shabbos/Yom Tov modes.
There are numerous issues with using a regular electrical urn for Shabbos. One of the main issues, is that most of the time the urn has a thermostat, and when atr is taken out if it, it cause the temperature in the urn to go down, which activate the thermostat to turn on the heating element. Another issue is that many urns have a shut off switch, for when the water level gets too low. I am attaching an article 01בטאון_אספקלריה _ חודש אדר תשעט written on this subject, (see pages 12-13) which explain things very briefly.