The latest quantitative risk assessment of hydrogen in a domestic context is that slightly greater explosion risk is outweighed by the slightly lower fire risk. Hydrogen has a wider explosion range... but most natural gas explosions are from small leaks accumulating basements or low spaces in houses which hydrogen won't do. It could instead accumulate under the roof but roofs are almost never sufficiently gas-tight to hydrogen to allow for substantial accumulation.

Also, many leaks are in the mains or services under the road. Natural gas will flow along the outside of the pipe and through the soil and end up in the basements of nearby buildings. Again, hydrogen would not do this, it would diffuse up through the soil and disperse in the atmosphere.

The big change is to boiler enclosures. These are currently designed to limit voids sufficiently to prevent natural gas explosions which require a minimum cell size of a meter or so to explode (regardless of concentration) rather than deflagrate. That same size for hydrogen is about 5cm so that is the largest acceptable void within the boiler enclosure which requires re-engineering of the way parts fit together and the use of non-h2 permeable foams and plastic spacers to avoid unacceptable voids.