@Netpass: I suppose the config you have shown in the question is a wg.conf file to connect to the Fritzbox from the RUT, right ?
If so, on the RUT wireguard -> General setup menu:
- set the Private key field to KCdPa.....
- let Public key empty
- keep the default value of 51820 for Listen port
- set IP addresses to 192.168.10.1/24
In wireguard->Advanced Settings:
- set MTU to 1420 at most (but check the MTU of your wan interface and substract 80)
- set DNS servers to fritz.box
Then create a new instance (a peer) if you haven't already done so and edit it with the pen.
In General setup:
- set Public key to jLkg ....
- set Allowed IPs to 192.168.178.0/24
- set "Route Allowed Ips" to On
and in Advanced settings:
- set Preshared key to cyij...
- set Enpoint host to xxxxx.ddns.net
- set Endpoint port to 58991
- Set Persistent keepalive to 25
- let Routing table empty.
Save&apply, and check via ssh or CLI that the tunnel using the "wg" command.