Metal Bill Boards are an easy way to tame it, but alternative stone traps may work (Argentavis Trap, 2x2 door way trap). I highly recommend Honey, easy to get and is practically kibble, but mutton works fine.
In Mobile version, megatherium can be resurrect on the obelisk after killing it in the dungeon (plase in mobile, where you can have battle with bosses). It doesn’t live in normal world. In mobile it eats an old kibble: baryonyx egg+raw fish+potato+mejoberry+fiber. It is very important information for mobile players!
To make honey last practically forever, make a fishing rod and equip honey, that is about to spoil, to the fishing rod, then un-equip it. It should refresh the spoil timer. Does not work with leech blood. Tested on PS4.