sudo dnf install -y obs-studio-plugin-vkcapture.i686

in both f38 and f39 does not pull any package,it says not found, however it does exist and is built in koji:

https://koji.fedoraproject.org/koji/buildinfo?buildID=2294539

https://koji.fedoraproject.org/koji/buildinfo?buildID=2294536

obs-studio-libs is required to build and use obs-studio-plugin-vkcapture.
obs-studio-plugin-vkcapture is used to video capture vulkan and opengl games and applications.

the 32 bit packages are needed to capture 32 bit games/applications.

For more context both the x86_64 and i686 packages are needed. The i686 package is used for video capture for 32 bit games, and although the package name is 'vkcapture' (for vulkan), it also captures opengl so it's usage also applies to older 32 bit native linux games running opengl, not just proton/dxvk with Vulkan. Without this only the 64 bit plugin is loaded and therefore only 64 bit games can be captured.

Opening ticket as discussed in Fedora Release Engineering matrix channel.