This popped up in a pot near my front door.
I know you wise ones will know! The inverted shape of the leaves is throwing me.
Could easily be wrong, but thought you already nailed it as the introduced a. lividus shown in the earlier extension link. The notched/cleft leaf apex seems more like this a. blitum/lividus Eurasian branch. We do occasionally see redroot pigweed (a. retroflexus) around our yard, but the notched leaf was a new one - was impressed that you made the connection.