I think FCEVs are only viable for buses and aviation. Toyota and Hyundai put a gamble on FCEV cars - but that is so far a flop without the backing of Big Oil. Toyota’s reasoning was to protect the Japanese auto industry from Korea(Hyundai-Kia) and China(BYD and Geely) and they laughed off Tesla. It’s too difficult to have infrastructure for retail gaseous fuels - only Australia, Japan and Hong Kong have that down with LPG(autogas) and CNG. CNG/LNG/LPG tanks in cars, trucks and buses are condemned after 10 years of service - typically a compressed gas tank(like a scuba/fire/CO2 tank) needs to be hydrostatically tested and certified every 5 years.

The problem with burning hydrogen - the NOx emissions are higher than burning fossil fuels. In a gasoline or diesel engine, that can be mitigated with exhaust gas recirculation and selective catalytic reduction(used with EGR on diesel engines, Mercedes/Daimler Truck & Bus calls it Bluetec) but CO/PM/HC emissions are much lower.