These Tentacle System components work with lego bricks. It includes a base and a grip.
The Tentacle System allows you to create ad hoc stands and holders using a variety of connectors and grippers. This part lets you attach those ad hoc stands to a Lego model or attach a lego model to a tentacle.
These print without supports as two pieces each. You can superglue the two parts together easily by simply aligning the edges.
The reality of FDM-printed Lego parts is that they don't fit nearly as well as actual lego bricks fit because the printer has an accuracy of about 1/3mm and the pieces are designed for an accuracy much, much smaller than that. It would work with a resin printer.
For an FDM printer you might need to scale up or down the part that attaches to lego bricks. The other part (the grip or base) must not be scaled or it won't work with the tentacle system. In both models the part that attaches to the lego bricks is quick to print by itself so you can try a few different scales to see what works for your printer.
You can learn all about the Tentacle System here: https://3ddoodle.com/tentacle-system/