Quick message...
First, if you open modrana-qml, and then lock screen and keys, it will regularly unlock-activate the screen - why?
Second, if you open modrana-qml, and switch to window-manager (where multiple windows are displayed), modrana-qml will close itself with Segmentation fault, quite quickly (well, no more than ten minutes).
Neither of these problems happens with modrana-gtk.
[Edit]You could also consider adding OpenSeaMap as one of layers.[/Edit]
Best wishes.
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Per aspera ad astra...