Empty conduits on the property - ideas? - It's not too late yet :)

just because the property is larger doesn't necessarily mean you need more sprinklers. Only greater throwing ranges are needed, unless it is very convoluted. Even with 100 sprinklers, we're talking about 200€. For something you have for many years. Much larger amounts are spent on more pointless things during house construction.

Which drip line is recommended? There are also installation kits for that, but with a shut-off valve, etc. Is that necessary? The set for 100m dripline costs a whopping 280,- which I find steep.

No, you don't need a shut-off valve. You only need the fittings to go from your distribution line/circuit to the drip line. And of course an end cap. Drip line is not cheap. I have had good experiences with the 17mm XFS drip line. It costs about €1.10.

I have to connect the Hunter distribution box to an outdoor water tap for the time being. However, I can't find the correct coupling from 25mm PE to 1/2" water tap thread. Maybe someone here has a tip on the exact name of this part?

Use the connectors from Gardena. On the side of the faucet a 1/2" thread and then one with a 3/4" thread.
Then connect to.

Connector with MA Ø 25 X 3/4" Unidelta 77020-250
There may also be a direct reduction. I haven't found one quickly though.

It has a direct 1/2" external thread: connection with [AG Ø 25 X 1/2"] Unidelta 77020-2505