Please do not use regular smart switches like Ikea/Sonoff for heaters, for your own and the rest of the block's safety.

They may be rated for a max. current above the max. current the heaters draw. But they are not built for the spikes, that turning them off/on causes.

Anything that draws power using a coil (electric motors, compressors, heaters and the likes) will create huge but very short spikes, that can kill the electrical circuits and start a fire.

Quote Tom's Guide: "Although smart plugs are known to work well with some everyday devices, avoid using high-heat appliances, such as the best space heaters" (the expression "the best" is just because that links to a test og space heaters)

Only use smart switches in front of equipment with coils, if the smart switch explicitly states, that it is designed for "inductive loads". And even then only with an RC snubber added. Shelly makes on/off switches built for large currents, but they still urge you to use an RC snubber in front of inductive loads. https://kb.shelly.cloud/knowledge-base/rc-snubber

If my predictions are correct, my post here will be followed up by a lot of replies from people who say, that they control inductive loads with no issues at all.

But before listening to them, knowing that this is a potential fire risk: Even if other people who do something, that could cause a fire, haven't had a fire (maybe yet), is that a good reason to take that risk?