From googling apparently there is a option in gnome tweaks (Yes it should work on Budgie too). I can't remember if tweaks is installed by default or not if you can't find tweaks in the system menu install it via:
sudo eopkg it gnome-tweaks
Then apparently you can set mouse acceleration to flat as described here:
https://www.linuxuprising.com/2018/09/how-to-disable-mouse-acceleration-in.html