Is 19 degrees C an alright temperature to sunbathe on the beach?

borderline. depends on how sunny and how windy. Moving around and doing something would probably feel quite warm but laying on the ground is a different thing altogether. Also, 19 is the max, not the temperature the entire time, and often at the beach the air is a little cooler because of the nearby ocean. Although very nice temperature for a fall day, it is still a fall day. A bit chilly for laying on the sand, in my view. A perfect day for visiting the beach though if you want to wander around.

Warm enough to sunbathe but probably too cold to go swimming - we dont even get that temp here in Scotland during the summer time and we still go to the beach and get a tan, Good Luck

no way warm enough to take your gear off.

And the water will be too cold.

I would say 23+ is a good enough temp and ideally 25+ and sun all day

That's 66 deg F. A little cool for me, especially seeing there almost guaranteed to be a breeze of the ocean which will make it seem even cooler.