Comment by retSava
IIRC lego had two actual patents: the basic brick, and the classic figure. The brick is expired while the figure isn't. Hence you can find "alternate" bricks, but not figures. They do own a shitload of trademarks, and aren't afraid to enforce them (which they legally must or they risk losing the TM).
Fun story: my wife ordered a couple of those "alternate" sets, and none inflicted on Legos patent nor TM (no lego branding, not a copy of a lego set, etc). The Swedish customs acted on their own (baffling to me) and stopped the package, sent her a letter in stark wording to accept forfeit. She challenged this, then Lego's lawyers got in contact with us and, using the figure patent, claimed this was a copy and we should forfeit or they would sue her. Very harsh letter, very stark wording.
Left a very bad taste in my mouth, haven't bought any Lego (or alternatives either) since.
There is jazz improvisation handbook "Harmony with Lego Bricks" written in the 1980's by Conrad Cork in the UK. It's pretty niche. Conrad approached Lego at the time and they gave him permission to use the Lego name. It's written "LEGO(R)" on the cover. Those were more innocent times I guess. (edited for a typo)