In Flanders (at least where I’m at) we usually say I grec, but when doing math or reciting the alphabet, we say IJ.

Sound like igrek.

Usually same as our compound letter “ij”, similar but not quite how you’d prononuce the word “eye”. Less commonly it’s pronounced as “i-grec” (greek i) or “ypsilon”.

In Swedish I pronounce y as y. It has its own sound and doesn’t sound like another letter, so it can’t be written as a combination of other letters.

Üpsilon