Multipath TCP for Linux (2022)
Multipath TCP (MPTCP) for Linux, an extension to TCP that enhances connection redundancy and performance by utilizing multiple underlying TCP sessions simultaneously. This site provides installation guides, debugging tools, FAQs, and a list of apps supporting MPTCP, aimed at facilitating the adoptio...
https://dillonbaird.io/articles/mptcpbonding/
My main use case is multipath VPNs. The above article is a good review.
The current options are speed fusion from peplink, speedify, and mushroom networks. There's no good out of the box open source multipath VPN.
There has been discussion of wire guard extensions that do multipath UDP. There is discussion of quic based multipath UDP.
I think with a bunch of hand waving, you can get open VPN to use multiPath.