I’ve been using Magic Earth on my phone for the last little while and have been really happy with it (I have Organic Maps and OsmAnd installed as well). I haven’t found anything good for desktop that includes public transport navigation (my primary use case).
I don’t think Organic Maps supports public transport navigation yet, but since you mentioned it, just a note that OM is also available in beta for desktop.
They’ve got an option when routing for public transport but it just shows the walking route