That's why plural is the wrong term. No one uses LEGO as plural. What people do do though is use it as a collective noun - so "this is my lego" not "these are my lego" or "these are my Legos". And yeah it is opinion not supported but the company that LEGO can be used as a collective noun. For what it's worth I think I know where Americans found the 'S' that they like to stick on the end of LEGO. It's the one that belongs at the end of 'maths'.
Nope, LEGO claims people use it like fish or sheep, so these are my LEGO, like these are my sheep. Obviously wrong though, just like maths
Not that I care but the Lego argument reminds me of the GIF inventor trying to claim you pronounce it jif, to put it bluntly he doesn't have any say in the matter and as it's short for graphics interchange format using a j doesn't make the slightest bit of sense so I ignore it. Lego, Legos to me either works but I will say legos is actually in the dictionary as a plural of Lego.
Lego is lego, lots of lego is still called lego Maths is maths (not math) Its like words like pneumatic where you dont pronounce the p. Its just one of those words where for plural you dont add an S, Lego is lego !
Not in The Oxford English Dictionary. That calls Lego a "mass noun". (I do have a photo to prove it - but I can't get picture uploading to work in the Toucharcade app)