Hi all,
Just to give a feedback, i finally managed to tackle my issues. Changing the theme corrected the UI issue, as advised by @lnicola.
To correct SNAP, I had to delete every piece of SNAP file present on my computer and perform a full reinstallation. Now everything is clean is seems to work properly. Not exactely sure what happened, but years of installing softwares / libraries probably messed up something in my computer.
Thanks for your help