Don't eat it is right!
Even if I had a positive ID on that mushroom I would not eat a specimen that is so far gone. That fungi is way past its prime, It is too old, which not only makes it hard to ID but also hard to enjoy eating it.
However, since I do suspect it is an oyster I would watch for more, and you could try a spore print, which you could cultivate, then of
course you could just toss it back into the garden in a pile of woodchips.