Forgive me if this has been said before, but after searching 'how to" i could not quickly find such.
As many others, I wanted to 2x my video speed, but found that audio pitch increased to chipmunk.
This is not a detailed how to but a direction pointer.
What i found was i was able to use Audacity to import audio form the video and add two “Effects” #1 “Change Speed” to match what you want the video to be, then #2 “Change Pitch”. For example if i want 2x speed, then my appropriate pitch was -50%. Export the audio and use it in Shotcut while muting the original video.
Thanks and good luck.