I've flown at two gliderports that also had skydiver operations. One
used good radio procedures and I found it no problem to keep an eye out
for the jump plane - they'd announce approaching the drop area. The
other used a drop area well away from glider operations and was never a
problem.

At least skydivers are well trained and have a good incentive to avoid
flying into a glider.

It's ultralights I hate - the flying equivalent of snowmobiles!