Marinix. It’s aimed at mariners & sailors. Small and fast but not full featured and it uses a weird kernel implementation. It does however have customized Muplex which I ripped off for the next dristro which I love :
Navigatrix - OpenCPN, zyGrib. SSB / HAM control, tidal info, radar and AIS overlay. RTL-SDR AIS, PACTOR 2 soft modrm, and so much more. It runs my main navigation computer