Several sources say it's not a grey area at all. They're illegal for privacy reasons:

www.theportugalnews.com/news/2023-09-10/why-are-da...#

Thanks for providing the article, @Bromptonaut! The privacy law in Portugal is confusing because dashcams are illegal, but CCTVs are allowed (with some restrictions). I guess the use of DSLRs and phone cameras are restricted in Portugal as well, where you’re not allowed to take a photo or video of someone’s private property like their car or house.

"not allowed to take a photo or video of someone’s private property like their car or house".

Doesn't seem to apply to Google Streetview.

Here's what I found regarding Google Street View, @Chris M: It automatically blurs license plates and faces, not just in Portugal, but anywhere else in the world www.google.com/streetview/policy/. It seems like a pretty robust system, although there could always be occasional glitches. Maybe I could use this technique when posting my photos from Portugal, just blur out the license plates and faces?

That’s an interesting point about Germany’s approach to dashcam footage, @Brit_in_Germany. Thanks for sharing the info on Germany’s stance; it gives some food for thought on how different countries are navigating this issue. It’s a tricky situation for visitors to Portugal who might be used to using dashcams in their own country.