This topic is related to Is RuBisCO going to be added as an enzyme/organelle.
Considering that Luca will start from an anaerobic environment, we need some anaerobic autotrophic.
We have the current ways about chemoautotrophism: Rusticyanin requires Oxygen, Chemosynthesizing Protein directly converts hydrogen sulfide into glucose.
I think Chemosynthesizing Protein is amiss, its hydrogen sulfide is directly converted into glucose without consuming energy. But in reality, purple sulfur bacteria use hydrogen sulfide as hydrogen source to synthesize glucose with light energy. This process does not release oxygen.
Before the emergence of oxygen producing photosynthesis, Sulfate(SO4-) is the most widely oxidant in primitive ocean, the primitive ocean is filled with hydrogen, ammonia and hydrogen sulfide. They are excellent energy source and more efficient hydrogen sources than water until the increase in oxygen concentration suppresses their concentration. But there is no hydrogen gas in the current game, ammonia is limited to only reproduction, and hydrogen sulfide is directly converted into glucose.
I tend to separate energy supply, hydrogen source decomposition, and carbon sequestration. hydrogen source decomposition consumes ATP and produces important NADPH, which is provided on carbon sequestration.
I have an idea that hydrogen source decomposition is limited to use ATP from energy supply in adjacent position, such as photosynthetic pigment(Chlorophyll, Carotenoids, and Retinene). It would help to achieve that similar to oxygen photosynthesis in cyanobacteria and sulfur photosynthesis in archaea.[Additionally, we should consider that thylakoid has the overall effect of using light energy to decompose water. But it is the only intracellular membrane structure of bacteria, so we should pay special attention to it.]
edit: Nitrogen in acidic and reducibility primitive oceans should exist in the form of ammonium Instead of ammonia.