There are a bajillion apps for Android covering every imaginable thing, and often 20 apps that do the same obscure thing. Yet I can't find a trangulation app. We used to write our own 25 years ago. This is used in radio direction finding to locate a transmitter or noise source.
You walk or drive to a location and take a bearing on the noise. The app places a pin on the map where you are and draws a straight line representing the bearing you measured. Then you walk or drive some distance and take another bearing. The app puts another pin and another line.
Where the two lines intersect is the target. Simple. With radio it's a good idea to take several bearing to improve accuracy.
I can't find any app that does this simple thing. I can't even find a decent app that lets you draw arbitrary straight lines on an OSM map.
Sheesh.
From the answers I've received, there are at least two apps that do this but run on Apple only. There are also at least two apps for Android: the one you indicated here and one called Sigtrax.
I installed Sigtrax and it appears to be well done and works smoothly.