Undo Redo | Cut Copy Paste Delete Select All | Inspect | Block Element

I've long had a Mac with a Firefox install. For as a long as I remember, the spellchecking (when entering text in textedit boxes) has never worked. But that's been ok because I only had the Mac for an xcode/iOS development job, and did most of my web browsing (using Firefox) elsewhere (Linux machines running Debian) and spell checking always worked fine there. However stupid typos slipping through when I was using Firefox on the Mac eventually led to me wanting to get to the bottom of this. It wasn't so much simply that the spellchecking doesn't operate... it's that the right-click menu is strangely devoid of anything but Undo Redo | Cut Copy Paste Delete Select All | Inspect | Block Element (that last one from uBlock Origin plugin). '''NB''' there were no "Language" or "Check spelling" items there at all, which are the first things I'd look for on my other machines if spellchecking went awry. I tied all the usual diagnostics/fixes: remove plugins (uBlock Origin is the only one I ever use), new profile, "refresh firefox"... none of it made any difference. I went through a ton of items on this site by nothing seemed to be quite the same problem and the suggested solutions didn't work for me. I eventually decided reinstalling from scratch was the only option: binned Applications/Firefox and Library/Application Support/Firefox and did a fresh install of the 119.0 download. But no joy. I'm typing this in it right now and there's no spellchecking happening and the right-click menu is just the same as it was before: devoid of "Check spelling" or "Language" items. The Firefox settings "Language" section does show "English (GB)" selected, and "Check your spelling as you type" enabled. But spell-checking certainly isn't happening in any text box I'm using. (I've attached a screenshot of what the right-click menu does look like, when I bring it up in this text box I'm typing in now.) I'm not a "Mac native" so I'm not sure what else on the system could be messing things up. In the system settings the Trackpad is set to "Click with 2 fingers" and certainly brings up a menu in Firefox text edit boxes... but it seems odd that the Language/Spelling-related items I'd expect to see are missing from it. I'm totally baffled. Any help much appreciated.