The article mentions thermoelectic generators only make sense when used with fossil fuels, they aren't very useful with electric heating, as presumably the user then already has access to a grid or some other more powerful form of renewable electricity.

Ehh, from what I can tell based on reading through the summaries he provides on the later episodes of that series, he appears to be advocating for Anarcho-primitivism, even going so far as to say cities, and even modern medical care and medicine are a part of 'modernity', and thus unsustainable. He is not far off from a doomer, but instead is spinning it as 'letting go' and mentally accepting that we'll collapse into a more primitive state, which he sees as more in-line with positive ecological practices and ultimately a good thing. Some of his language even comes off a bit cult-y, IMHO.

I think there definitely needs to be severe economic degrowth, an end to capitalism, and a heavy focus on regenerating our natural environment and the species that live within it, but we absolutely do not need to have some mass die-off event to have a sustainable planet, we just have to stop the practices that are killing it.

"net zero energy use" isn't a meaningful term. We can talk about net zero carbon as it is part of a cycle where carbon both has sources (burning fossil fuels, respiration of animals) and sinks (forests, oceans, wetlands, artificial carbon capture) so the two sides can balance to zero on net.

There is no "net" when it comes to energy usage, it is either used or it isn't. There is nothing fundamentally wrong with using energy, in harnessing energy is what allows increases of standard of living fundamentally. We need to stop the negative externalities of certain types of energy generation (primarily fossil fuels).