If governments forced miners to use solar energy only, would Bitcoin become more sustainable and valuable, or would it reduce mining capacity drastically?
This is not possible, all governments in the world can not think the same. When China banned bitcoin mining that time in 2021 or so, it was an opportunity for country like Kazakhstan which encouraged bitcoin mining and the country is using coal for energy generation. Know that if a country say something, another country may say another thing.
What if some big economy made it mandatory to do mining only using solar energy ? Will it have any impact on bitcoin ?