Comment 7 for bug 591886

There's a relatively easy workaround - you can run dpkg to install the package and force it to overwrite the conflict. If I remember, it's something like this (from a terminal):

sudo dkpg -i --force-overwrite /var/cache/apt/archives/linux-firmware_1.34.1_all.deb

You might need to change it for the particular version of the linux-firmware that you're getting the error for (I copied this location from an error posted above).