ok many thanks will try. So you mean just on uplink e.g. Port 8 (TL-SG108PE) - (VLAN 1t, 10t, 50u ), or should I leave vlan 50 untagged on all port...

Hello, connecting Openwrt and Netgear switch I select tagged for all VLAN 1t, 20t on both sides for each Port. Between Openwrt and TL-SG108PE, I need to leave the connected Port 8 on TPLink switch...