Alright here's what I found using a "clean"(no addons/extensions) browser and downloading mods from here.
Mega - no popups, ads or extra downloads
Pixeldrain - has ads but no popups or extra downloads
Google Drive - no popups, ads or extra downloads
Workupload - Has ads and 1 popup but NO extra downloads
Racaty - Has ads and annoying popups but NO extra downloads (also only 1 mod uses it)
In conclusion:
There are no requests for me to download a downloader on any of them.
There are some ads which don't really matter unless you click on them.
Workupload seems to have 1 popup when clicking download but that's easily closable.
Racaty is annoyingly popup-heavy without browser addons but is only used by one mod in this thread afaik.
If you download a popup blocker then all you've got are some ads. Here are links to it for
You must be registered to see the links
and
You must be registered to see the links
.
I'd be curious to hear what other peoples experiences with it are when following the links the modders have posted here.