It doesn't look like the peruse git repo is marked active anymore. Did that recently change? kdesrc-build will refuse to build inactive git repositories so that it doesn't accidentally download needless repositories when including dependencies.
I'll leave the decision up to you, but I think this should only be added if
peruse's presence in playground is simply temporary, and that it's currently planned to move to kde/kdegraphics or similar. There are a whole lot of modules in playground/base alone, so I want to be careful of how many of them get added to the default KF5 build.
If it's not planned to move to kde/kdegraphics, you could still add it as part of a commented module-set (probably in kf5-applications-build-include) to show off the playground git repositories. Something like:module-set playground-modules repository kde-projects # Uncomment the following line to build software programs that are still under development #use-modules peruse kio-mtp end module-set