mini M1 won't download .dmg files from various sources. Permissions? Sticky Bits?

Looking at various files in the usr directory you see very many with special permission bits set. These are hard to turn off and impossible to change via the "System Settings". Downloads begin, then after a second or two the download stops and will never try again. Changing System Settings - no difference. Removing sticky bits from Download directory sometimes works. Why all these extended file attributes???