Change Shimano Ultegra R8000 crankset
Officially, you would need to use the corresponding GRX front derailleur.
This is because the GRX crank uses a wider chainline, which is the distance from the center of the bottom bracket to the midpoint of the crankset's rings (hat tip to the late Sheldon Brown for the link).

Shimano road double cranks use a 43.5mm chainline (for example, the R8000 crankset specification page reports this). As reported in the first link by Bikerumor, GRX spaced the chainline out by 2.5mm. Velonews reported (Lennard Zinn's column) that Shimano did this to better accommodate wider tires.
Unofficially, you might be able to use your existing front derailer, as Shimano's specifications are often conservative. You would move the limit screws accordingly. However, it isn't guaranteed that you would be able to move the derailer's range of motion outwards enough to shift, and it's possible you might experience more chain rub than you otherwise would. Given that front derailers are cheap, I'd recommend just buying the corresponding FD if you must go this route. Alternatively, you could consider a third party crankset, but these tend to be pricier than the corresponding Shimano option. Also, rider feedback tends to indicate that Shimano chainrings have better shifting than most alternatives.
It may be worth considering if you actually want an endurance road bike like the Endurace, or if you want a gravel bike. Many of these bikes do just fine on the road, and they are more versatile than pure endurance road bikes. Naturally, the answer could certainly be that you want an Endurace with sub-compact gears.
The type of front gearing you're trying to achieve is called sub-compact gearing (where &quot;compact&quot; usually means 50-34 chainrings, and &quot;sub&quot; denotes anything smaller, including 48-32 rings). Shimano has not yet addressed this niche of cycling, i.e. road bikes with sub-compact cogs. Campagnolo offers this type of gearing in one groupset (12-speed Chorus), and I suspect they plan on trickling it down to Potenza and Centaur (but I have no inside knowledge). SRAM appears to be moving to address this with their new Force AXS wide-range gearing options.