I've deleted my profile in ~/.mozilla/firefox and built a new one from scratch.

I removed the installed version of Firefox ("Firefox-ESR" in Debian's terms) then reinstalled it.

The image I showed you was of the new installation starting from an empty profile. The truncation exists even though no addons or extensions are installed.

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can try Firefox from the official Mozilla server if you currently use a version from the repositories of your Linux distribution to see if it behaves differently.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

The same issue mentioned in the thread below.

https://support.mozilla.org/en-US/questions/1437094

The same issue mentioned in the thread below. https://support.mozilla.org/en-US/questions/1437094

There is no evidence of truncation in that thread, the screenshot shows "Manage extensions" at the bottom which is the fullest extent of the panel.

Does it still happen if you set the environment variable MOZ_ENABLE_WAYLAND=0?

What desktop? What version of Firefox? Not able to replicate the issue. see screenshot

Operating System: openSUSE Tumbleweed 20240118 KDE Plasma Version: 5.27.10 KDE Frameworks Version: 5.114.0 Qt Version: 5.15.12 Kernel Version: 6.6.11-1-default (64-bit) Graphics Platform: X11 Processors: 16 × AMD Ryzen 7 5825U with Radeon Graphics Memory: 62.1 GiB of RAM Graphics Processor: AMD Radeon Graphics Manufacturer: HP Product Name: HP ProBook 455 15.6 inch G9 Notebook PC

I downloaded the binary for 121.0.1. The problem does not exist there. However there is no easy method to add the Firefox repository to Debian like there is using the add-apt-repository command in Ubuntu. Why can't I add the repository to Debian?

Seems like something went wrong with the ESR version.

No repository for Firefox from Mozilla. Your distro version will get updated when they push it and the Mozilla version will get updates from Mozilla.

I'm running ESR on Windows, Mac, and openSUSE with no issues. What Desktop? X11 or Wayland? Currently on my old mac running 115.6 with no issues.

The text in the first screenshot looks rather large. Is that a (Hi)DPI setting in the OS or is this done otherwise in Firefox as that be part of the problem (i.e. the panel height isn't adjusted) ?

My video card is connected to a 4K TV. In order to get a reasonable resolution on KDE, I have to accept the 4K resolution and use the scaling factor to make the text large enough to read. By default I have the scaling set to 275% (System Settings > Display). None of the drop-downs are truncated in this version even with this scaling. (There is an issue with the size of the cursor: https://gitlab.gnome.org/GNOME/gtk/-/issues/5567)

"this version" = 121.0.1 The truncation problem doesn't appear in this version.