Plasma Mobile deserves the same degree of integration with desktop PCs as we have with Android phones using KDE Connect.
The kdeconnect-kde repo contains a WIP implementation of a Kirigami frontend for KDE Connect. To build it the CMake flag EXPERIMENTALAPP_ENABLED must be set to true. It is basically functional but lacks some features that the Android implementation provides. Those must be ported to C++/Qt(Quick). This will also be beneficial for the desktop2desktop and non-Plasma KDE Connect experience. Note that KDE Connect is intended to work outside of Plasma, so Plasma-specific implementations should be avoided where possible.
For most of this you won't need to run Plasma Mobile. You can develop on any Linux distribution.
Some possible tasks are listed as subtasks to this task.
Knowledge requirement: Basic understanding of C++, willing to learn Qt/QML