What speeds are you seeing on ZeroTier, if you don’t mind my asking? You can do something similar with Tailscale which is running at probably 80% of OpenVPN speed on the routers I’ve tried.

It would be better if mwan3 played nice with the various setups (Tailscale has been reworked to fix the issue, but I think something about gl-inet’s implementation in 4.X is non-standard, which makes it not work again). It’s really a shame it isn’t supported natively, given that the CLI syntax is simple and the functionality is great.