I got notified since my post was linked here. Upstream MPTCP should be there on kernels 5.6 and newer. It's not enabled by default though. Maybe you didn't search properly on menuconfig? If I recall correctly, for upstream MPTCP, the option is called Multipath TCP, not MPTCP.
First I use the Ysurac build and it is a great work on his part (I have two links to my house). However, it is stuck now at the v5.6 Kernel due to the upstreaming of MPTCP. That's not a good situation I think. Also it is cluttered with a lot of things I do not understand and I doubt work well or are needed to solve this problem in the USA. As I am more or less getting started with MPTCP it hard to penetrate all that code.
I have also looked at the work of @arinc9 and it is also very cool. Thanks for this great work which I have read many times. It proports to be lighter weight but now also stuck due to the upstream it seems.
Many of the changes in the Kernal between 5.10 & 5.19 are MPTCP related so this whole area is under active development.
As an OpenWRT enthusiast and tinkerer I am interested to explore it. Not asking for it to be in the default builds but was trying to learn how it could be included under menuconfig. Perhaps I did not search appropriately. Let me go back and check.
@jow I understand, not supported in LUCI or uci. But this functionality is very cool and right in OpenWRTs wheel house so I can image a future when a plugin exists for it. Now that it is in the upstream it seems to be getting more realistic.
I was unable to find any MPTCP configuration options in menuconfig. I searched for both "Multipath" and mptcp and found nothing. So now I am confused. If v22.03 is based on kernel 5.10 how can this option not be present?
Because you didn't add the packaging to add those configuration knobs, yet. That won't do itself, without anyone interested in those features putting in the necessary work.