Hey fellow european!
Tinytronics.nl -> Pi4 model B 8GB: 87€ and in stock. The 4GB model is 68€. They also have orange Pi for a higher budget.
Kiwi-electronics.com -> Pi 4 model B, 4GB? 63€. They also have all the pi accessories you could want.
If you are going to use paperless for important documents, and if you want to not lose data for sure, get a 1TB cheap HDD or something and a USB3.0 adapter. SD cards will eventually fail.
Otherwise, get an old used laptop 2nd hand. I used an old HP probook G1 laptop for about a year for my server. It didn't use much power at all.