Just on the KDE front, I’m assuming you’ve optimised your KDE set up for your PC?
If not, first open your Settings app and in the search box type “Effects” - disable all the fancy desktop effects.
Next, if you’re on X11, go into the “Display and Monitor” section and disable compositing (you can also temporairly disable this with Alt+Shift+F12 to see what impact it has). This option is not available in Wayland; but you may be better using X11 if you don’t have a dedicated GPU? I’m not sure I’d be messing with Wayland on an old laptop; I’ve had serious issues on a high end PC - definitely improved with 6.1, but I’m using X11 still.
But KDE 6 isn’t as svelt as KDE 5 was, so even optimised it may just not be up to the job.
XFCE is a good shout, and should run nicely on a 2013 laptop.
According to Wikipedia, A028 is an open/free version of Albertus and widely available on Linux.
You could also download versions of Albertus itself to use in KDE - there seem to be lots of versions.
Fonts are easy to install in KDE, if what you want is not in your package manager then download the font files and install it with the Font manager tool in Settings (just look for Fonts). You can install fonts from files you have downloaded or download more from the KDE store (I don’t know if A028 is in the store).
It’ll be available immediately in LibreOffice, and you can also use Konsole settings to use the font for your terminal.