I suppose that true breakthrough would be a development of a plant or fungus "base" that would be able to create animal cells. So something like bamboo rhizome

I suppose that true breakthrough would be a development of a plant or fungus "base" that would be able to create animal cells. So something like bamboo rhizome constantly growing an meat trunk, using either photosynthesis & minerals (plant-based) or plant mush (fungus-based) as source materials.