Something minimally useful can probably be had for about 1000 EUR.
Something like ASUS F17 JVQ MP: https://amzn.to/3MTONgv
That’ll run No Mans Sky just fine, and let you get started on UE5.
More RAM would help the most on top of that. A step up on GPU would be the next step. To do those upgrades, you end up at 1200-1300 EUR in price.
A desktop you put together from parts is likely to let you upgrade it as you go, so it may be better if you don’t need to move around.