This morning, there was an update to firefox-esr (115.3.0). After installing it, the toolbar has changed so that addons are no longer accessible from the mobile screen:
In particular, I have found the “Mobile View Switcher” extremely useful, but now there seems to be no way to access that button on the mobile screen.
Maybe the FF mobile config is not working with the new version of FF?
It is still working, but since we have new elements on UI, the CSS mobile config needs new edits. However, if you installed all fixes on ~/.mozilla/firefox/[YourProfileCode].default-esr/userChrome.css it could be overwritten (you should check this).
I’ve filed a bug report on your behalf: Config doesn't work with Firefox ESR 115 (#8) · Issues · Librem5 / debs / firefox-esr-mobile-config · GitLab
Hmm, I have to give a look into it later. It seems they changed some more UI-functionality than I realized.
Update: It’s another point for “Enough is enough Firefox” thread. They implemented that Addon-Button that cannot be removed. Instead they removed the functionality to put addons inside the overhang menu and call it “exciting user interface change”.
This major update also ushers an exciting user interface change in the form of the new extensions button.
Right now we can access the addons, but we lost the control about the windows. Some addons can be used in portrait view, others can be used in landscape view and if we’re unlucky, some could have a to big window in both directions.
It’s really a problem since Firefox 115esr come with performance improvements (much faster start up and initial connection to websites on L5) and Firefox 102esr is not supported anymore. So sticking on Firefox 102esr would be what we want with addons in mind, but anything else speaks for Firefox 115esr. Hard to say what’s the solution for our issue.
I don’t have installed thes CSS files at all, but after the today update FF is not reacting at all on any click on menu menu items, It’s UNUSABLE COMPLETELY Can I somehow rollback this update. @dos o @joao.azevedo , please help me.
Mozilla is very annoying with Firefox always breaking user configuration 
I’ve lost count how many time I had to solve the tabs to bottom issue, this one (115.3.0) broke it again, and I’ve seen other post about other broken things in the UI
Seems like they never heard of “WE DO NOT BREAK USERSPACE” at Mozilla 
It does not help to re-install FF again, move away ~/.mozilla/firefox and restart FF; it does not react on any menu clicks.
Sounds like the common Phosh-bug where you need to push the physical power button and go back to Firefox. But I think you already tried that, didn’t you? Just asking to be 100% sure that’s something else/new.
I don’t know this procedure. What I should do in detail?
Nothing complicated. Push the power button to make screen black (logging out of your local account), push it again to turn on screen and login. Everything should be fixed.
Phosh has a major bug where it can loose the target of the shown application (can include Phosh itself). It happens because the system “think” the phone shows up other windows (can be other apps or just additional windows of same app) and tries to match your touch input with the wrong windows. And I also had it with Firefox 115esr, so I thought you may run into same issue. The steps above usually work. In few cases it’s maybe also a good idea to restart the app, but there is usually no need for.
I reinstalled an older version with
apt install firefox-esr=102.10.0esr-1~deb11u1
and lost all my bookmarks. But at least it works again.
I did the same and restored the .Mozilla folder from a recent backup and everything is back to normal. I have also put firefox upgrades on hold until the issues are resolved.
Everything appears to work in landscape mode so that appears to be the workaround if you need to use these buttons.
Ok, but awkward as I usually have portrait mode locked on my L5.
Landscape mode just disables all modifications, but fix nothing. Flickering is there, addons cannot be put into overhang menu and even touch input gets disabled from time to time (I had same issue as guru on some sessions and now I think it’s a new problem of FF and not that Phosh issue).
I got enough for now and also reinstalled the old version. Just don’t forget to restore the .Mozilla backup (like tomoqv said) or you will run into issues or even crashs.
We definitely need better improvements than just CSS-fixes.
There is no need to put Firefox updates on hold. Just install upstream mobile-config-firefox, which already works with 115: postmarketOS / mobile-config-firefox · GitLab
You need to change firefox to firefox-esr in lines 8 & 9 of Makefile · master · postmarketOS / mobile-config-firefox · GitLab before running sudo make install.
If anyone is interested, I just submitted the September 2023 Update for Firefox-ESR 115 on my Mobile-Friendly Firefox Customizations post.
@linmob, I think you suggested in a previous post that these forums are not the right place to post such code. I agree, but there are no better options for me. I am not interested in creating accounts on github, gitlab, or any other similar sites
As per the MPL-2.0, you and others are free to share and modify the code wherever you want. I’m not a developer/programmer. I just like to custom configure my browser-of-choice and thought I’d share my work with the world in the most convenient-for-me way I could. I have also linked to my forum post on kbin so that more people could see it (if it federates properly).
I think you have no fix for addons, do you? Otherwise 115esr is still not usable for some of us. I was looking further into about:config setting and found a method in 109 to enable overhang menu extensions again, but those options don’t exist in 115 anymore. 
The tabs can be fixed by using Ctrl + T using the Terminal layout to open a new tab. After that, you can freely swipe them like before.
I may or may not bother to do something about the rest of the UI, but if I do, I will provide another response with solutions to this thread.