Try taking an old git version and applying only the patches you need.

Ok

The reason I use VirtualBox is simply, that it is the recommendation in the developers guidelines of the project

That's a perfectly reasonable requirement. The problem here is that solution space is like the JavaScript ecosystem. There are more solutions than you can count and no two developers ever agree on everything. Everyone eventually settles down on one solution or the other based on their personal preferences. That's why I thought it was important to give you an overview rather than a definite solution.

I just want to add that VirtualBox is a backend to 'Vagrant'. Developers usually depend on Vagrant, rather than fiddle with VirtualBox directly. Vagrant takes care of some low-level VM configuration on its own and consistently recreates the VM every time with little fuss. You will need a configuration file for the VM (Vagrantfile), either readily available or newly written. I recommend Vagrant rather than direct vbox due to its convenience. However, I'm not pushing it further since I can't judge your options better than you.

I am pretty sure one can isolate some things using docker-compose, but it can be frustrating if you want to get into the project codebase and then have to do so much infrastructure stuff.

Certainly! That's what tools like vagrant are meant for. The only problem is that it replaces tediousness with choice fatigue!

I don't have a GUI in my container which I need of course to run my IDE and the software itself.

This is where the convenience of tools like VM, devpod, etc shines. However, you can also implement this solution manually with VMs or Docker. It's simple - bind mount the source directory on host into the VM/container. Then you can edit it using devtools and IDE from both the host and the VM. Tools like vagrant and devpod manages this for you.

However, the situation gets a bit tricky when you want to use GUI applications inside the VM/container. That involves mounting the X11/Wayland socket from the host into the VM/Container, doing the correct UID/GID mapping and setting the correct file permissions. Developers usually don't do this manually since it's tedious. However, some tools manage that too. I don't remember which one, off hand.

Thanks again for your friendly way of explaining things, much appreciated.

Glad I can help! Take your time - there are a lot of tools to explore, unless you're on a mission. Good luck!

Is it legal? There may be alternatives with plausible deniability.

That makes me wonder! All these new GPU uses are enormous energy hogs. Is gaming like that too?

It didn't look like a submodule reimplementation to me. Subtree is more of a submodule reimplementation. This is more like a language-agnostic package manager (like cargo, npm, etc) that downloads and caches source packages.

I wish there was something more interesting to do there.

What do you do on the yggdrasil network?

The OP can make the same argument after replacing sudo with doas or su.

I have serious doubts about that due to the role of early Ubuntu in popularizing desktop Linux. For many including me, Ubuntu was the first taste of GNU/Linux and it was a breath of fresh air compared to the contemporary clumsy and cumbersome distros like Fedora. Only Ubuntu from those days has any resemblance to the experience we expect from desktop Linux today.

The problems at Canonical seems like a systemic institutional issue, probably related to egotistic management with temper issues. That of course means that Shuttleworth is the source of those personality disorders. But still...

Conduit might be an option. It's still under development. It's also lightweight due to Rust (instead of Python as in Synapse).