Tried to install a .deb package but I was always getting:
dpkg: error: dpkg frontend is locked by another process
I couldn’t find any answers after Googling and no process was using dpkg.
I don’t really know if this was a coincidence but:
sudo dpkg --configure -a
Did the trick!
Comment down below if this fixed your problem or it was really a coincidence
Update: As mentioned from Vlad in the comments below it was really a coincidence. “Just wait for some minutes and should be working fine”