You just said "large". I would consider any project with 10MB or more of source "large". Firefox is certainly large by that standard, but so is openssl. If your standard for "large" is "has at least as much code as Firefox", then according to you, the Linux kernel is a small project.
openssl is a vital part of the web, but it is a small tool
You consider 61.7MB of source code "small"? (That's for openssl 3.3.2, and may not include some rust code that isn't in the gzipped main code package.) I think maybe you need to recalibrate a bit.
A whole bunch of non-user-facing projects providing vital libraries that are largely ignored until something blows up in people's faces, as happened with openssl some years ago. Some of them contain quite a bit of code (for example, ffmpeg, which underpins a lot of open-source media playback software). Among browsers specifically, Pale Moon has been around for years, is maintaining a lot of code no longer carried by Firefox along with a fair amount of original code, and has no cash source beyond user donations, which might stretch to paying for the servers in a good month.
The projects with corporate sponsorship, or even a steady flow of large donations, are in the minority. There's a reason the xkcd about the "project some random person in Nebraska has been thanklessly maintaining since 2003" exists.
Money isn't important. Some complex software is, in fact, maintained by unpaid volunteers who feel strongly about the project. That doesn't mean it's easy (in fact it's quite difficult to keep the lights on and the code up-to-date), but it is A Thing That Happens despite being difficult.
What is important is the size of the codebase (in the case of a fork, that's the code either written for the fork or code that the fork preserves and maintains that isn't in the original anymore), the length of time it's been actively worked on, and the bus factor. Some would-be browser forks are indeed trivial and ephemeral one-man shows. Others have years of active commit history, carry tens or even hundreds of thousands of lines of novel or preserved code, and have many people working on them.
If you're interested in doing the tech equivalent of a party trick (except that it's less interesting to watch), go ahead and try. You'll probably just end up reinstalling almost every package on the system that differs between the base distro and the offshoot. Harmless, but also pointless, since you could just have installed Debian from the get-go and saved yourself a lot of trouble.
There are a whole bunch of Very Silly Things you can do in the Linux world that aren't worth the effort unless your income relies on the creation of niche Youtube vids. For instance, it should theoretically be possible to convert a system from Debian to Gentoo without wiping and reinstalling. I'm not going to try it.
My primary icon theme and widget style are 20+ years old and not flat in the least. You can still have that look and feel on a real computer if you want it (but you may have to compromise elsewhere or do some extra work). On phones, all bets are off.
Dunno what your issue with that icon pack is, but I'd bet there's a good chance it can be solved with a few file renames or symlinks if you care enough to bother.
Most people are not obsessed monomaniacs with room for only one interest in their lives. That means that most Linux users are interested in things other than free software, so many will choose to "dress up" their computers in ways that showcase their other interests, and may use material that is not under copyleft licenses to do so. If this causes you anxiety or confusion, you may want to speak to a mental health professional. Seriously.
I ended up setting up custom themes for multiple different widget sets to get a true black background. It was easy for most QT variants, not too bad for GTK2, really awful for GTK3 because it doesn't have proper documentation for manual theme creation, and I haven't tried to tackle GTK4 yet.
Because they all need different configs (and the window manager title bar etc. may need yet another one), it's difficult to give suggestions unless you tell us which terminal and window manager software you're trying to theme—the requirements for a Gnome session are different from those for something like fluxbox. Some terminal software even has its own built-in theming support.
TDE. Functional, stays out of my way, but still reasonably full-featured. The development team is dedicated to adding useful features while keeping the original look and feel, so I don't have to go hunting for settings that have inexplicably moved or changed defaults every time I update. It doesn't support Wayland, but I'm Wayland-neutral (that is, I have nothing against it, but I have nothing against X either).
Yet another, "well, yeah, technically it has security ramifications, but I'm not admin'ing any multiuser machines, so I'm not losing any sleep over it" bug.
I have at least four libraries, then, it seems. (My ex-librarian mother estimated ~3000 twenty years ago based on board-feet of occupied shelving, and I've only acquired more since.)
Gentoo supports either configuration, as it does with a lot of things. My systems were installed with split /usr and I have no intention of changing that, because the merge adds no value for me.
Um, if your primary use is typing accented letters, why don't you just set a compose key? The character sequences you need to type are much more intuitive, and you don't get this type of problem.
In my case, I have scroll lock (the most useless key on the keyboard) set as a compose key. To get "é", I type scroll lock, then e, then '.
You can set a compose key using setxkbmap, for instance setxkbmap -option compose:sclk. (If scroll lock isn't to your liking, there are a number of other modifier keys that can be used instead—list here, starting around line 810.) You can also specify it permanently using X configuration files, although I don't know the exact method.
The GPU doesn't care about the CPU, or vice-versa. AMD is probably better value for money right now if you're intending to replace both CPU and mobo, but Intel will work.
The reason you don't see AMD CPU + nVidia GPU in premade machines these days has to do with corporate contracts, not interoperability. Before AMD bought out ATI, it wasn't an uncommon combination.
Even if the original issue had anything to do with ISOs, he's way overestimating the level of protection on many install ISOs, in my experience—they're just disk images, and presumably all the files read off them are passing through Ventoy itself. Even if you find one that performs some kind of verification, easy enough to change a jump instruction to a no-op somewhere in the machine code guts of a file as it passes through Ventoy, and prevent the verification from executing. (The difficult part is figuring out which instruction to change, but people have done it before.)
It can’t inject anything into the ISO files at rest without bricking then, and I don’t know if an OS that doesn’t verify it’s own image before booting.
As far as I can tell, this is not talking about ISOs installed using Ventoy, but precompiled blobs of things like Busybox that are included in the Ventoy install package. It's an important distinction. The developer could bundle a tampered blob, include in the documentation the checksum that matches that blob, and then if someone checks with the upstream project and calls them out, say something along the lines of, "Oh, they must have withdrawn that release," and replace it with an untampered blob. If they don't fight to preserve the tampered blob, they might even get away with it.
-o PubkeyAuthentication=no should only work if the server is configured to allow password auth at all. I believe the advice these days is to disable password auth completely for security.
Configuring captive portal wifi without network manager or any aids beyond what's provided by wpa-supplicant. Eventually I gave up, since it wasn't really that important.
Adjusting freetype so that it works more-or-less the way I want it to, because the maintainers hate anyone who disagrees with their current hinting algorithm and make the setting as opaque as possible. I would prefer it if they allowed me to have hinting on some fonts and exclude only the ones that were designed to be pixel-aligned, but unless something's changed recently, that option isn't even offered.
I don't know how Debian's solution works, so I couldn't say for certain. Gentoo usually installs the different package versions to their own directories, and there are methods for selecting a "system python" (or lua, etc) which is the target of the /usr/bin/python symlink. Other versions have to be called with qualifiers (for instance, python3.10). Python libraries installed through the package manager may install to one or several versions depending on the content of a couple of environment variables, and applications that need python can request a specific version if they need to, or accept the system python if they don't care. (Note that python2 is no longer eligible to be the system python—you need at least one python3, although 2.7.18 remains in the package repository and can be installed as well if you really need it.)
Of course, if you're not a programmer, you can leave the defaults for everything alone, and most of the time it should Just Work.