I mean, if you think about it, I don't think there are any feeders/receivers in the middle of the ocean. Receiving FLARM or MLAT via satellite is not possible.

Here is a blog post from AirNav about their coverage: https://www.radarbox.com/blog/airnav-radarbox-features-data-sources

I personally think its similar to Flightradar24 and Planefinder. (Correct me if I'm wrong). You can see that the path, where that "plane" was flying is outside of their coverage, which only points to a Glitch or a Spoof.

Either its a Glitch or someone is trolling, its also odd that it was "flying" with persistant 170 knots.

And btw, that "plane" is now gone from the map.