Welcome to the forum. Here is the USA, we get engines with hose barbs so we use 5/16" (8mm) flexible rubber fuel hose to USCG spec.
The engines in Europe all get the compression fittings for copper tube. If you want to use approved rubber fuel hose, I suggest that you use a 3" piece of 8mm copper tube in the compression fitting and fit the rubber hose on to this and clamp it securely. This works well.