Solar iBoost has been around a while so should be pretty good.
I have one that I can’t remember the name of which is OK.
I’ve also got an Immersun at the beach place (which is entirely electric) and that’s excellent with lots of options, such as remote boost*
Once the water is hot it sends spare generation to a dedicated heater which helps to keep the house warmer than it would be otherwise.
I’d get another if I could but they’re pretty expensive now 🙄
* I monitor the hot water temperature using a Raspberry Pi and if the it isn’t hot enough at 4pm then it switches on a wireless socket that applies a small voltage to a port on the Immersun which activates the boost function.
So theoretically, even on a cloudy day there will always be enough hot water for everyone in the evening.