I've been looking at this project for a while which may be interesting to you: https://github.com/Ysurac/openmptcprouter.

I recently bought a property where I cannot get a full fibre connection, but I can get 150-400 Mbps using 5G. I've been thinking about using dual 5G connections and tunneling my traffic via mptcp to a VPS to aggregate the connections.

It was recently enabled in the Home Assistant ‘HAOS’ kernel. https://github.com/home-assistant/operating-system/pull/3248

I hope some apps will start using it :)

one example on openwrt http://www.openmptcprouter.com/

Good point, the last version (v0.60) is using the upstream kernel by default. I just added it in the list: https://www.mptcp.dev/apps.html#misc

Whats the benefit of an openwrt router supporting mptcp?

I'd think support on web servers and mobile devices would be most important...

I got fiber run to my neighborhood, and for a while, had a 1gb coax connection and a 1gb fiber connection. I used openmptcprouter to aggregate my connections through a droplet and I effectively had a 2 gigabit internet connection. I would have stuck with it, but having a datacenter IP for your home network really doesn’t work.

Except TCP is just a bad protocol to start with for tunnelling, because packetized data has to be delivered in-order, and head of line blocking messes up congestion control algorithms in the tunnelled data.

Link aggregation and redundancy