This patch is for master, but can be applied to the 19 branch....
Basically, the problem is with the Realtek Giga Switch driver that is not supported by Openwrt yet. We are working with Openwrt to include support for this chip.
Thank you for the images. I am using 19.07.02. I received kernel version mismatch error after openvpn-openssl package installation attempt. Please update the images to match kernel versions for this package. Thank you for your help.
FYI, the DSA driver for the Realtek rtl8367s got merged upstream today. It might arrive with kernel 5.18. Once that switch driver is available, it might not be too difficult to have C5v4 support merged.
This driver does not offload forwarding and all traffic between LAN ports still goes through the CPU. Maybe we can add the offload support before OpenWrt really uses it.
I have a branch with 5.15.17 kernel and dozens of backported patches that can generate a working image. There is a hack to disable all mediatek resets that prevented to boot the image. Mediatek Ethernet also have some trouble with checksum offload and incompatible dsa tag. I'll test changing the Realtek CPU tag position to the end of the packet. Maybe Mediatek will be happy with it. For now, it is disabling checksum offload.