Powered solar heat pumps sanitize themselves once a week if temperature doesn’t reach 70C at least once. Same for heat pump boilers, they are usually set to 50C but goes up to 70C weekly.
On solar, there is always a downstream heater that can heat cold water to 60C+ and must be set at least that high for legionella. My setup is like that, unpowered solar tank for free heat if available, and gas boosts it up to safe temperature and does all the work in the winter.