i think this is just a mindset thing for low end developers. dx11 = cheaper to compute thinking.
i ran lumen in dx12 and dx11 with proper project configs to tick all the low end switches. no visual difference. i haven’t measured actual performance, tho. it just runs nominal 60 or 48 on my rig (i’m not pushing fps on my cpu). i think even the rdna2 gpus should be able to handle dx12 lowend. maybe there are a couple of fps to gain in dx11. i dunno for sure tho. i can only google. i don’t have a steam deck. nice to have a legacy switch tho. tbh. eases the mind. 