I already have about three mice I’m not using, so I wouldn’t even need to buy one. Mice are a pain in the rear to use on the go though. And what’s even the point of a laptop if you aren’t using it on the go? You might as well get a desktop machine at that point. My Librem frequently gets really hot, so having a full desktop would be better if not on the go, as there’d be more air between components and there’d be bigger fans, both of which would help keep the machine cool.
I just tried the GNOME Tweaks thing you mentioned, and it doesn’t allow both left and right virtual mouse button to be used at once. It seems like whichever area of the touchpad is touched first is the only one that takes effect. You say that touching both gives a middle click, which doesn’t seem to actually be the case, but regardless, the default settings makes a three-finger tap into a middle click, so the middle click is kind of available, but not really because you can’t combine it with other click types and you can’t choose your own desktop. Using multiple mouse buttons at once isn’t possible on Librem hardware. Speaking of not being able to choose your own desktop, I’ve been getting fed up with GNOME anyway, as stated, meaning that GNOME Tweaks doesn’t really help. I’m stuck using a desktop I’ve hated for years because the Librem one-button mouse doesn’t work on lightweight desktops that aren’t expecting asinine, one-button mice.
There seems to be an inverse correlation when it comes to desktops. The ones that support “fancy” hardware that thinks removing key hardware features and emulating them in software are the same ones that force other unwanted features on users, even when thousands of users complain about the same feature, and refuse to provide a way to turn those features off. So I can have a desktop that allows me to performs tasks reasonably, or I can have one that supports asinine one-button mice. It doesn’t seem that having one that does both is an option.