In addition to what other people have said about gdebi, I'm surprised it's not there by default in Pop. I thought it was there in pretty much all Ubuntu-based distros (except where alternatives are used).
I totally get not wanting to use the terminal for this purpose. It's pretty rare that I download and install a .deb, but when I do, it's nice to just click it straight from the browser and not have to navigate to my download folder in the terminal. And given how rarely I download and install .deb files, I have to look up the command every time.
I can't find anything to anything to support their assertion that a E5300 is a "Pentium 2", but the chip is from 2008, so it's not relevant to your situation. Maybe they meant it was a Pentium from the Core2Duo time, but that's still not a "Pentium 2".