Definitely a sign that the saprotroph is winning.

Yeah an old Laetiporus cincinnatus is what it looks like to me.

Gymnos and other cacti can only be grafted to other cacti, never a euphorbia. Often the rootstock used for grafting cacti is the Selenicereus “dragon fruit” cactus. This is because it has a faster metabolism and can make the scion cacti grow faster than normal.