"They were going to go to France on vacation."
Translation:De skulle åka till Frankrike på semester.
Both de and dem are pronounced as dom. Some people spell them that way too. It is acceptable, but not standard usage. Many Swedes struggle with the difference between de and dem, so replacing both of them with dom would make sense, but that idea has not won general acceptance yet.
Hehe, with which huge amounts of native English speakers struggle.
The de/dem difference is a remnant of an older case system that no longer exists, and they're pronounced the same. I don't think it's that weird that some struggle with it. Not everyone can be a linguist. :)