Wikimedia OCR currently uses the free Tesseract OCR engine (which only supports printed text) and the commercial Google and Transkribus OCR engines.
The free kraken OCR engine supports printed and handwritten text. Like Tesseract, kraken is used in the OCR-D project for OCR of historic prints. It is much slower than Tesseract, but sometimes gets better results and would be the only available non-commercial OCR engine for handwritings.
I suggest to start with my free models for German print and German handwriting (they are not limited to German, but can be used with other languages which use Latin script as well), but there exist many more models, for example for Arabic or Hebrew script.
I already have implemented a prototype and sent a draft pull request for Wikimedia OCR.