I use Firefox on two desktops and a Surface tablet.
A few weeks ago, on the tablet, I became unable to highlight (or therefore copy) any text on Firefox. I can do so on the desktops, and the functionality is still there on all other applications on the tablet, so it's a Firefox thing.
I have been unable to find anything about this online. Could there be a setting that got changed or something else?
Yes, and same with Microsoft Surface Book (Windows 10 and 11), and same problem with Thunderbird. FF and TB seem to be the only apps suffering from this limitation, eg, Chrome works fine. FF, TB and Chrome all interpret holding down the pen as scrolling (like the hand icon in Adobe Reader). The difference is that Chrome allows selecting text by pressing the side button (which corresponds to the Right mouse button, I know it's not totally logical, but at least it works).
BTW, Scroll-Lock key makes no difference, nor does the "Let me use my pen as a mouse" setting in Windows 10/11.