If you have issue building please try to downgrade asio to a version before 1.34.0, this a headers-only library so packages only rely on it as a build-time dependencies.
Arch Linux has unfortunately updated asio without testing if packages using it would build and websocketpp happens to not work with the newest asio.
For those who might ask why libva-vdpau-driver was added to conflicts.
It is the only way at package level to prevent the user to have segfaults because of this driver. This will not be fixed on OBS side since this is not an OBS issue.
The driver is only loaded with Nvidia cards.
Try libva-nvidia-driver if you really need Nvidia decode through VAAPI.
This package have some dependencies with version check, it will allow you to rebuild the package only when your system is correctly updated. This feature is not enabled on Manjaro.
If you have any issue, please before commenting rebuild this package (a clean build) and try again to make sure it's not because of a library update.
Pamac has a messed up dependency checker, use another AUR helper for the first install.
This AUR package provide OBS with all the missing feature except Twitch, Restream and YouTube integrations.
More explaination here: https://ideas.obsproject.com/posts/1558/
It provide any dependency needed for Wayland support.
I'm quite active on OBS discord server (don't PM me directly).