Download firefox from the mozilla website instead of using the ubuntu package and this won't happen. Or disable auto upgrades.

A few weeks ago, I read that vertical tabs landed in Brave's nightly, but still behind a flag. So, there seems to be hope.

Maybe I'm missing something or set some settings years ago and have forgotten but I have zero problems with restarting Firefox after an update from my package manager.

I regularly have 2-4 Firefox windows with dozens of tabs in each and a "You need to restart" button press takes like 4-5 seconds max to close all windows and reload them all with all of my tabs as they were. The most I have to do is stick each instance on the right workspace.

Granted each tab will reload when opening it but if I'm updating my OS packages I'm probably not exactly "in the zone".

I am using opera with “tree tabs” extension, but afair there is a similar (or the same?) extension for chrome. Although they do not hide the horizontal tab bar.

Firefox unfortunately copied Chrome's behavior and you have to resort to a user script to hide the horizontal tabs.

Edge has vertical tabs built in. Many other browsers can be made to have vertical tabs with plugins.

Edge is not free. I wouldn't seriously consider using a non-free application for something as essential as everyday web browsing.

You can't really have usable vertical tabs in Chromium via plugins either, unless you're content with wasting a lot of horizontal space for an ugly sidebar and vertical space for uselessly duplicated tab bar.

Firefox is the only actual choice I'm aware about.

Using Firefox definitely supports the existence of a free browser. Loss of market share is the #1 threat to the continued existence of a free browser. Beyond the obvious (if a tree falls in a forest, crushing the last copy of the code for a browser that has zero users, then was it a browser at all?):

    lower market share =>
    nobody testing against the free browser or fixing site breakage =>
    quirks (bugs, underdefined specifications, nonstandard features) of other browsers becoming required for a functional Web =>
    free browser is no longer a browser of the actual Web.

Marketshare is important, default search engine revenue is based on usage.

It’s not really ‘free’ if it has to produce ad revenue.

It is irrelevant to it being free.

No it isn’t. The direction of development is controlled by the need for funding.

The direction of development is irrelevant to it being free.

If it is controlled by corporate interests, it is not free.

Being controlled by corporate interests is completely orthogonal to being free. A lot of Free Software is being controlled by corporate interests and there's nothing wrong with it.

Given that the issue of Firefox being forced to restart primarily happens on Linux, I doubt Edge is an option for them. Though I have to concur that Edge has one of the most stable and smooth vertical tab implementations around, most of the plugin-based ones are more fully featured but much less reliable.

Edge has been released for Linux a while now... not that I know anyone who uses it, but it's available for those who need it.

I use it, and it's decent. And more in the vein of "it's not google" though I do slightly prefer the chrome dev tools to the modifications that Edge has made. I don't like a lot of the "helpers" for shopping though. And definitely don't like the article wall with ads that are really hard to block/script out.