Trademark law leaves no space for that. The Lego Group has to actively defend their trademark. That means a name like LegoGPT is really on the obvious end of 'don't do that'.
1: Never, ever, sell modified Lego bricks: https://www.brickfanatics.com/lego-wins-court-case-against-c...
Also, they don’t tend to go after fan-made things like this, based on some googling they typically throw the book at counterfeit producers who are eating into their profits.