Look at instant hot water heaters to colocate near the fixtures; they don’t have to be powerful enough to provide hot water for the entire fixture use, just the time between when fixture use starts and hot water arrives from the primary heat appliance.

Fossil gas tankless units are nice because they can be installed on the exterior of a home and are maintenance free, but emit CO2 and can be expensive depending on your gas costs (they’re better for seasonal dwellings imho). Ideal combination is resistive instant heaters at points of use with a heat pump water heater for the whole dwelling.