sudo ufw allow proto udp from any port 3702 to any
Note: Ensure your machine is on a trusted network.
I am assuming filter rules for samba and wsdd have already been applied. If not, apply them with the following commands.
sudo ufw allow samba
sudo ufw allow wsdd
Restart the firewall with 'sudo ufw reload' and windows PCs in the network should become visible in Dolphin. Hope this helps!