I downloaded OSM data for Austria from Geofabrik and converted them with ogr2ogr into a SpatiaLite database so that I could use some Google Maps style sheets I found.
Until here, everything worked very well.
Then I wanted to add a shapefile with some points I tracked in nature as well as a orthophotografic I bought at an official government store.
That works also, but the OSM data on the one hand and everything else on the other do not match. My own data is about 50 meters farther east than it should be to match the correct point on the OSM data.
I looked for on-the-fly transformation, but as I read this feature isn't optional any more since version 3.
I use QGIS 3.0.1 and as CRS WGS 84 (EPSG 4326)