As part of my ongoing efforts to update and re-publish my QGIS plugins, I have just uploaded a new version of the prepair Processing provider.
Along with the fixes focused on Qt6 compatibility, this plugin also went through some refactoring driven by the changes in the latest versions of the prepair and pprepair tools and the availability of the native QGIS API to run external processes.
This Processing plugin provides tools to easily fix "broken" geometries using prepair and pprepair tools developed at TU Delft. It allows to repair single broken geometries (like self-intersections or dangling edges) according to OGC Simple Features/ISO 19107 rules and repair a set of polygons to form a valid planar partition without unwanted gaps or overlaps.
Check the plugin page for more details and installation instructions.