Hello Kind readers !
After reading many posts and tyring many solutions, I decide to write here.
I hope it may help improving this enjoying Ubuntu Mate... and myself !
I report you :
a(nother) "non working touchpad" problem, after installing U.Mate 20.04 (dual boot with Windows 10 64 pro, on a besides partition).
NB : F6 button or "touchpad-indicator or desabling mouse don't change anything.
a(nother) "installing PacketTracer 7.3.0" problem, because of "qt-at-spi unsatisfied dependances"...
Thank you for your enlightning answers !