Hello, I had inkscape 1.3.2 installed before, then I installed inkscape 1.4 beta version with this program installed, but the old user interface remains the same, how can I change it to the 1.4 beta interface? I uninstalled and reinstalled the program and deleted everything related to the program and reinstalled it, but the problem is not solved.

Before proceeding further, I'd reset the preferences. https://inkscape.org/forums/questions/getting-back-to-square-one-and-starting-over-its-easy/

thanks but I also tried this method and it didn't solve the problem

Did you try changing the theme in preferences?

1.4 beta and 1.3 version together, why is it writing both together?