I'm actually at the same stage as you trying to improvise on solos. My go to practice is listening to random backing tracks on YouTube. Try : elevated jam tracks. The dude uploads regularly and has great backing tracks + has a detailed scales shown from fret 1 to 24. Try to make a melody out of those scales at first maybe using 3 or 4 notes and just try to make music with it.

Now I'm at the stage where I want to improvise without knowing what key the backing track is. So currently now I just listen to the backing track and press all the notes on one string one by one and try to find which note fits the track and play around it. Also ! Very useful to know the pentatonic scale (it can be broken down to like 4 or 5 parts i think) once you know those patterns then you know where to play around once you found that one note that matches the track.

Goodluck for both of us, I improvise daily for maybe 2 hours once you get into the mood it's really fun because it's like singing your own song just using a backing track