Gas boiler efficiency and solar thermal energy in new buildings, what are the advantages?

And district heating is exactly something that would be too unpredictable for me ;)

Of course, it always depends on the provider... There are also district heating providers who charge enormous amounts and produce heat in an "old-fashioned" way...

In principle, district/near heating is one of the most sensible things for me... A large combined heat and power plant that generates electricity and heat from renewable energy sources (biomass, landfill gas, etc.) is superior in terms of efficiency and environmental perspective to most heating systems... plus, you don't need space for a heat pump, etc., there is no noise pollution, no device can break down, and you hardly have any investment costs (which usually have to be financed!)

By the way, the dependency with heat pumps is in my opinion similarly large... sure, there is free electricity provider choice but if everyone raises prices by 30% you’re screwed ^^
and if you have followed energy policy recently it is clear that electricity prices will go up significantly... an increase in district heating tariffs from our provider hasn't happened for years and remains stable at 3.5 cents/kWh

Basically, both options are possible for a Kfw 70 house. Both systems mainly differ in their energy source, different installation locations, and investment costs. You have the choice between NATURAL GAS and electricity, inside the house (gas condensing boiler) or on the property (heat pump), and an amount of around €5000 (natural gas) or significantly more!
Here, taking into account one's own user behavior, the location, the building physics conditions of the property, and the possible future technical and economic developments, a decision must be made. Quite a few framework factors that a builder cannot possibly consider all. Expert advice from a specialist, an energy consultant, is required here if it is not or cannot be provided by the person who prepared the energy saving regulation certificate for the property.

Best regards
Erik