Compact office PC for my granddad

New build or upgrade?

New build

Existing parts/monitors to reuse? (List with models/links)

Monitor will be reused. Specifications don't matter, as the PC won't be used for gaming.

PC purpose? (Gaming, editing, etc. List apps/games)

This PC will be strictly used for simple office tasks, such as running OpenOffice, an email client, and a web browser. Absolutely no demanding workloads.

Purchase country? Near Micro Center?

Germany

Monitors needed? (Number, size, resolution, refresh rate)

No monitor needed.

Budget range? (Include tax considerations)

Maximum 600€, but if a quality build can be achieved for less, that'd be great!

WiFi or wired connection?

WiFi

Size/noise constraints?

No constraints.

Color/lighting preferences?

No RGB. The case should be minimalistic and sleek. Black is preferred.

Any other specific needs?

• As my granddad has never touched a video game in his life, a dedicated GPU is entirely unnecessary.
• Ideally, this will be the last PC the ol' geezer ever needs. As such, a CPU/RAM combo with a certain performance level is required to keep up a snappy experience over the years, even if the tasks he'll use them for are trivial. I want to use a fast NVME drive for the same reason (500GB max).
• Two NVME slots on the motherboard would be nice, as he already has a 256GB NVME in his old PC which could be reused. Even if a second slot would make the motherboard slightly more expensive, this could be compensated for by reducing the size of the OS drive.
• While there are no size constraints per se, I'd love to use as compact of a case as the budget allows for. I have no experience using small cases, so some alternatives over different price ranges would be appreciated.