Implementation of fwupd package within PureOS Byzantium (I’m no SMA, just simple user) is very specific one. You can introduce yourself to it (related update errors you have had) over this post of “mine” (actually through related links about), very recent one.
$ man dpkg − explains things - I’d coarse say (add) that dpkg package exams your system internally and for
$ man apt − explains things - I’d coarse say that apt exams your system compatibility with the entire/current and particular Linux environment.
For example executing sudo dpkg --configure -a is rare thing (command) that you’d ever need again (probably wasn’t needed at all) with PureOS but still very important one making sure that you’ll boot into your Librem 14 system again without any issues. It can still be executed (from your side) from time to time and if no output there you can 
.
Exactly and if you like you can put here output of sudo apt-get -f install.
Also, please remember this procedure in order to actually see which Linux packages are about to be upgraded:
-
$
sudo apt update -
$
sudo apt list --upgradable -a -
$
sudo apt upgrade
And every time you see that older linux-image-5.1X.X-X-amd64 is about to be upgraded be aware that your last command will be sudo reboot into brand new (just installed) Linux Kernel.
Thanks for your post! It tells me you’ll be just fine (takes time but not much for you), IMHO, as you carefully approach to everything you do.