Hi,
Please rest assured to use it. The entire European region uses the DE hardware country code, which has no impact on the use of the router and there will be no potential issues.
Of course, if you need to modify the WiFi country code, you can make adjustments in the Luci page.
In the luci interface Netwok-> Wireless then edit the intefaces. In the middle of the displayed page the country can be choosed.