I did the same song and dance with 3 hygrometers for a while. Like you said, they would hardly ever match and became waaaaaay more of a chore than I was willing to deal with.The Govees are the main reason I got away from even watching humidity.
Someone recommended them and I saw others had them. I bought one. I liked it. Liked how small it was and that you could just toss it in and track from phone.
I decided to buy another 3 pack. Just to use in all the hovabator hatchers but to also spread around in my pepsi-bator to see how different the humidity may be from top to bottom.
I quickly realized none matched each other. I didn't like the idea of having to calibrate them but you could so that's what I did. I don't know how many times I did the salt test to get each one of them correct.
I put them back to work and figured things would be good but mine never held steady. Often I put all four of them side by side in one of the hatchers or on the dresser and I'd be lucky if two matched. It just seemed like constant recalibrating them. Honestly at this point I don't even know where they're at.
I don't know I might give them another shot and get some more but I might find a different brand.