Thermodynamically you start with ~55MJ/kg available if you were to oxidise the methane.

Then you end with 750g of carbon that would give you ~35MJ/kg were you to oxidise it or 26MJ. And 250g of hydrogen that would give you 120MJ/kg or 30MJ

If it were 100% efficient and free then for the cost of the input methane you could get the same amount of thermal energy with a solar panel or wind turbine and a resistor.

As far as ways of greenwashing fossil methane go, it might actually have some potential positive effect, although the hydrogen produced will not be competitive except as backup energy.

As a thing to do with waste-emission methane it might be better than burning it. You’d still need some way of storing the hydrogen that is competitive with overbuilding solar + 4-12hr batteries (none presently exists).