This question comes up a lot… You can add a WMS via the “add data” feature in the map tab and then save that map as a basemap. To use that in your SMART Mobile pacakage, select the basemap you’ve saved with the WMS when configuring your mobile package and be sure to set the bounds and min/max zoom appropriate to your site.
I’ve created a PDF with some simple instructions to walk through this because I always have to remind myself how to do this too. They’re attached here: Add a WMS to SMART basemap.pdf (1.3 MB)
The WMS I’ve seen used most commonly is Open Street Maps: https://ows.terrestris.de/osm/service?
I’ve also recently come across this one which looks good too: https://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv?
It would be great to hear if anyone else as any good WMS recommendations!