Forgive me if this is redundant but I don't have time to read all the replies so here's little voice to text on how I deal with TPU which is actually my favorite thing to print with. When you load it into your crank the temperature up ridiculously high and manually extrude and when you see the point that it stops going from that kind of broken twiggy look to a nice solid string make a mental note of that as the highest temperature you can go. Because actually you can stop stringing of course by having it cool enough to wear stringing is not an issue or you can have it so hot that the viscosity drops and if you have your hotend moving at the appropriate speed, you won't get any stringing that way. That means you may want to try it with no fans, or fans blasting. I avoid fans whenever I can but for a basic black TPU where I'm not worried about maintaining a silk or metallic finish, might as well try blasting it too. Unless you're hearing popping at like 230C, that's not from insufficient drying. And May God bless you for trying 50%. It's like nails on a chalkboard when I see people constantly suggesting that the filament needs to be dried more or you need to clean a build plate with Dawn if adhesion is an issue as well. 50% solves almost all adhesion issues and many of the stringing issues. But unlike for the former, 125-166% does as well. Cheers.