Merging multiple vector layers to one layer with multiple geom types with QGIS

I have a situation where I need to merge a large number of spatial files into a single output with a free tool like QGIS, rather than FME or Alteryx.

Along the lines of this post: Merging multiple vector layers to one layer using QGIS?

However, I have some point features, some line features, and some polygon features. This rules out outputs like shapefiles, but anything else is fine like GML, TAB, or a database.

Is there anyway to do this in QGIS?

Every process or model I try makes a shapefile at some point which means this can't work.