I have a similar problem: my main DB can be split, but the “far” DB, where most of the big things ended up, only has a single feeder, so that cannot be split in the normal sense with two feeder lines, one essential and one not.
So I bought this, arrived on Friday:
It’s Tuya, which I like: really simple to get going, everything works together across brands, cheap, and you can “upgrade” to local control and Home Assistant if you want. There are eWelink / Sonoff versions as well.
It’s a motorized breaker, like you would get on an autocloser earth leakage. The current rating is very high when compared to relays. This one is quite configurable with selectable overcurrent, over/undervoltage, khw measurement, timers, etc.
So my kitchen DB will be split and the heavies are turned off when they should be over wifi. Not foolproof as a dedicated feeder, but it works. If your wifi & internet are on essentials, this will work fine. Better option would be local control, but you don’t need to start there. You can also go for a Shelly Pro, which has a physical ethernet connect with an external contactor, since the Shelly can only do 16A. (I actually bought a couple, so aircons go immediately when LS hits, stove if batt < 50%, etc.)
What’s also cool about this one is that you can configure the current limit, so the stove can go from “full current” normally to 1A during load-shedding. That way the gas-hob igniter still works, but it trips if you turn the stove on.
Tuya lamps to signal loadshedding are a dime a dozen. Detecting LS is also easy, just wire a Tuya in-wall switch on UPS power to a relay on grid power. When grid drops, relay switches and a scene takes over. You can do all of this from your phone and later upgrade to Home Assistant if you outgrow it.