Replying to my own post: the NOAA charts are now accessible in WMS and WMTS format. (The old tiles were discontinued.) I've tried setting up the WMS or WMTS charts in Oruxmaps, but was unsuccessful. Has anyone else tried?
Links:
https://www.nauticalcharts.noaa.gov/learn/encdirect/#using-the-map
Links:
https://www.nauticalcharts.noaa.gov/learn/encdirect/#using-the-map