Hi, pavelgl, thanks for the reply.
I was using the TAP device before(Bridge with New TAP Device), but I'm not sure how to "Attach the newly created TAP device to the "br-lan", in my OpenWrt Web configure interface, I don't see the choice options in your last image shot as you posted, so I do not know how to select the "tap_softether" to the br-lan's "Bridge ports".
What version of OpenWrt do you use? I'm using the I'm running OpenWrt 22.03.5 r20134-5f15225c1e / LuCI ce20b4a6e0c86313c0c6e9c89eedf8f033f5e637 branch git-23.144.07943-874ba1e under a Nano Pi R4S board. This is mentioned in my post: How to tweak the firewall of OpenWrt 22.03 to support Softether VPN server