The 2020s is the decade to decarbonise heat

Well, this report came out of Europe, where some grids (e.g. the French, Swiss, Swedish) are already very low carbon, and gas is more expensive.

But you do have a good point that heat decarbonization using heat pumps as discussed in this article really is dependent on clean electrical power.  My local grid (in the central US, in oil & gas country) has enough remaining coal power that a gas-fired home furnace is cleaner than using an electric heat pump, always for particulate pollution and sulfur, and sometimes for CO2.

The article is not great for helping with technical trade-offs.  It's seems like it's a marketing paper promoting consulting services for companies that want to install new (electric) heating systems.

As far as technical arguments for heat pumps as clean heat sources, I think they are weak until the grid is decarbonized.  They look particularly bad when they are treated as marginal load.  Heat is a very peaky seasonal load; even as grids become cleaner on average, power companies turn-on their oldest and dirtiest plants in order to meet marginal demand peaks.

Rather than heat pumps, I prefer district heat networks.  They can be powered by industrial scale heat pumps when clean energy is plentiful, and switch to using waste heat from thermal power plants when it's not. Insulated tanks can add cheap energy storage to allow use of off-peak electricity.