Camera / mobile phone for documentation in the workshop or construction site

A smartphone is too complex for the father-in-law.

But then there’s no more internet or cloud either. So either a pure camera or you take a decommissioned smartphone and put a SIM card in it.

For my part, I just take all the pictures with my phone. When doing dusty work, you’re usually not right there, so the snapshot at the beach is more problematic. But my Moto G8 also cost well under €1000 ;)
What I also find practical are pictures with the drone. I probably wouldn’t buy one just for that, but you simply get a different perspective.

Currently the builder - my father-in-law (retired and former master bricklayer) and I are building.

So no heavy use for any devices. Therefore, I don’t understand the question about an extra device. Every smartphone has to endure more in everyday life and on vacation than a few pictures on the construction site. There’s nothing major with dust either. Just a "simple" house construction.
So use your smartphone and take photos for your father-in-law. If he has no idea about technology anyway, he doesn’t need it.

Thank you you're somehow right. Then I'll buy a cheap smartphone.

Don't understand the problem. Just take your smartphone. I did that too. Even when grinding concrete. Nothing happens. Do you also leave it at home when you go on vacation? Car just sits in the garage and doesn't get driven?… If you're overly cautious, just take an Otterbox case.

so take photos with the iPhone (iPhone 7 for under €100 is enough), these then automatically end up in the Cloud (which you have access to) EVEN my 80-year-old mom can do that ;)

so take photos with the iPhone (iPhone 7 for under €100 is enough), they then automatically end up in the cloud (which you have access to) EVEN my 80-year-old mom can manage that ;)

Thanks sounds good - I'll check it out