Also what about the Manufacruring/production of devices to convert solar/wind energy to electricity and to mine bitcoins? It’s based on non-renewable elements (of course any chemical process is reversible given enough energy but Entropy still grows mercilessly) and requires a lot of extra energy.
EDIT: as far as we know, thermodynamically all energy will become heat at the end (although not sure if it should be called heat, since there will be no flux). However, we as humanity are/should be quite concerned first about decades and earth’s atmosphere/oceans (and connected parts) not millennia and energetically balance Earth as whole to come.
In principle energy from sun could also be stored in form of chemical bonds energy (as it’s the case for biomass) or even nuclear energy (yup, sun-powered nuclear fusion sounds unlikely but why not ;). Then biomass (less efficiently) or nuclei/atoms could be ejected from earth allowing to disperse sun’s thermal energy somewhere else.
So even if Bitcoin mining were to cause global electricity production to increase by an order of magnitude, it would still be a rounding error compared to the amount of global warming caused by the Sun directly.
Thinking about it thermodynamically, though, in a future where Bitcoin mining uses only excess solar and wind energy, it wouldn't be adding any heat to the planet because that energy would have become heat anyway.
[0] https://www.mdpi.com/1996-1073/12/16/3069/pdf