Created attachment 208703 [details] PNG of firefox showing mobileread.com forums. I'm running Firefox (firefox-70.0_3,1) on FreeBSD 12.0-RELEASE-p10, amd64. I'm completely unsure as to why, but on most websites firefox isn't displaying checkboxes well. I've attached a screenshot to demonstrate. In the Konquereor_checkbox.png screenshot, you can clearly see the checkbox in the Login area next to the "Remember me" line. On Firefox you can't see it. Just in case it was a plasma desktop thing, I also tried it on firefox in twm. Same results.
Created attachment 208704 [details] PNG of konqueror showing mobileread.com/forums.
Comment on attachment 208703 [details] PNG of firefox showing mobileread.com forums. Try disabling custom Gtk3 theme. Adwaita (default) should work fine.
Comment on attachment 208704 [details] PNG of konqueror showing mobileread.com/forums. Invalid comparison. Notice how buttons are styled. Firefox uses Gtk while Konqueror uses Qt. Unless Qt is confugured to use Gtk themes via compatibility layer (e.g., x11-toolkits/qt5-gtkplatform) both are not going to look the same.
I found the same (symptoms with check boxes etc.) following a recent round of updates to FreeBSD-CURRENT. Not limited to Firefox; Remmina and various other applications are affected. Affected themes include Breeze. I imagine that there's already a bug report somewhere. Worked around here with Greybird theme for GTK2 and GTK3. YMMV.
(In reply to Jan Beich from comment #2 and #3) Firstly, thanks for pointing me at the GTK3 theme. Moving it from Breeze to default has fixed the problem for me. My issue wasn't that they didn't look the same; it's that I couldn't see the checkbox at all. I used Konqueror for a comparison to show that I could see the checkbox in another browser. To be clear: until recently, I never had a problem seeing checkboxes in Firefox no matter which site I visited, including mobileread.com. Doing some searching around KDE's bugzilla it appears like the issue may be this one: https://bugs.kde.org/show_bug.cgi?id=412078
Created attachment 208753 [details] gedit and Firefox with Breeze
Created attachment 208754 [details] gedit and Firefox with Greybird Greybird theme – working around whatever bugs the window controls etc. in gedit; and the radio buttons etc. in Firefox …
I had same issue, but it was fixed in release 70.0.
(In reply to Dwayne MacKinnon from comment #5) <https://bugs.kde.org/show_bug.cgi?id=412078> was RESOLVED FIXED in February 2020. If the issue is no longer reproducible with Firefox 95.0.2 on FreeBSD, would you like to close this bug? Overcome by events, I guess. Thanks
(In reply to Graham Perrin from comment #9) I've confirmed that I can no longer reproduce this. Heck, I'd forgotten all about it, and at some point started using Breeze again. Marking it Closed, Overtaken by Events as suggested.