Developed under ISO/DIN specifications.
for 30 mm square tube. M8 screws with nut. All edges rounded, printed in PA6-GF. You can also use PETG. Table leg holder is a cheap option https://www.stahl-shop24.de/Stahl-Quadratrohr-30x30x2mm-1000mm.
Have fun, I would be happy about a like.