@PetarV Deco perhaps does not behave correctly because you assigned reserved address outside the DHCP range. One way to avoid the issue ("some new devices are unable to connect sometime") is perhaps...

@PeterGeelhoed The name "deco1" is statically linked to the IP address of a Deco? Does any local device use the Deco as DNS server?

@PetarV Some devices, such as Windows, show the duration of the lease they obtained. The out of range addresses were leased by the Deco, hence I expect they will be counted in the amount of assigned...

@PetarV You are incorrectly assuming that all used addresses are assigned to online devices. Once an address is leased to a device, the address remains "used" for the duration of the lease.

@LVDX what is your IPV6 Internet Connection Type & method to get IPV6 address?

@TDawgSmitty The DNS setting has no influence on the apparent "location". If you want to show a fake location, you better look at so called "VPN" solutions.