I wonder if there is a way to also make mod-specific entities of the same category this mod touches also freeze-resistant?

To name a few samples:
- big pipes https://mods.factorio.com/mod/FluidMustFlow
- thermoelectric engine https://mods.factorio.com/mod/corrundum

Interestingly, some mod-specific entities to work out of the box:
- https://mods.factorio.com/mod/pipe_plus

Sure, there is. This mod just sets properties on a few hand-picked prototypes. To generalize that, it would need to loop through all prototypes of some types and for some also check some additional properties (like whether the entity is supposed to make steam or molten metals) before setting the heating_energy property.

Here's the trivial code for all pipes and underground pipes:
for name, proto in pairs(data.raw["pipe"]) do
proto.heating_energy = "0W"
end
for name, proto in pairs(data.raw["pipe-to-ground"]) do
proto.heating_energy = "0W"
end

Thank you, I have a whole 2 hours of factorio modding experience but I guessed it was something like that. I'll modify so that all entities in the pipes, pipe-to-ground, storage tank, generator, and boiler categories are affected. This includes entities in the Corrundum mod and Fluid Must Flow because those large pipes are classified as storage tanks.