What's deadsnakes PPA

$ sudo apt update && sudo apt install htop

This shows:

https://ppa.launchpadcontent.net/deadsnakes/ppa/ubuntu questing Release
404 Not Found

It's that apt update is failing because you have a deadsnakes PPA configured for Ubuntu Questing, but that PPA doesn't provide packages for that Ubuntu release.

 

Check whether the deadsnakes PPA supports your Ubuntu release. If you're running a very new Ubuntu release (it looks like Questing, Ubuntu 25.10 development or a very recent release), the PPA may not yet have been built for it.

In that case you have three choices:

• Wait until the PPA adds support.
• Use the Python packages from Ubuntu itself.
• Use another installation method (such as pyenv) if you need a newer Python version.

 

 Run: cat /etc/os-release

You're running Ubuntu 25.10 (Questing). The issue is that the deadsnakes PPA does not currently publish packages for questing, so apt gets a 404 when it tries to update that repository.

Run: ls /etc/apt/sources.list.d/ 

You should see something like: deadsnakes-ubuntu-ppa-questing.list

Actually got: deadsnakes-ubuntu-ppa-questing.sources ubuntu.sources 

On newer Ubuntu releases, that's expected. Instead of the older .list format, Ubuntu now uses Deb822 repository files with the .sources extension.

You have:

/etc/apt/sources.list.d/
├── deadsnakes-ubuntu-ppa-questing.sources
└── ubuntu.sources

• ubuntu.sources is your official Ubuntu repository. Keep it.
• deadsnakes-ubuntu-ppa-questing.sources is the PPA that's causing the error.

 You can simply disable it by renaming it:

sudo mv /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-questing.sources \
        /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-questing.sources.disabled

Or remove it entirely:

sudo rm /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-questing.sources

Then install what you need: 
sudo apt update
sudo apt install htop

 

What's PPA and why it's needed?

 

A PPA (Personal Package Archive) is a way for developers to distribute software for Ubuntu outside of Ubuntu's official package repositories.

Normally, when you run:

sudo apt install htop

apt downloads packages from Ubuntu's official servers, such as:

• archive.ubuntu.com
• security.ubuntu.com

These repositories are maintained by Ubuntu and contain software that has been tested for each Ubuntu release.

A PPA adds an additional repository that apt also checks for packages.

For example, after adding the deadsnakes PPA, apt will search both:

• Ubuntu's official repositories
• The deadsnakes PPA

for packages.

Why use a PPA?

PPAs are useful when you want software that isn't available in Ubuntu's official repositories, or you need a newer or different version.

For example:

• A newer version of an application than Ubuntu provides.
• An older or alternate version of Python.
• Software maintained by a third party.

The deadsnakes PPA is widely used because it provides multiple Python versions that Ubuntu doesn't necessarily include by default. For example, on an Ubuntu release that ships with Python 3.13, you might use deadsnakes to install Python 3.11 or 3.12:

sudo apt install python3.11

provided the PPA supports your Ubuntu release.

Why did it fail?

Each PPA has to build packages separately for every Ubuntu release.

Your system is:

Ubuntu 25.10 (questing)

When apt checked:

https://ppa.launchpadcontent.net/deadsnakes/ppa/ubuntu/dists/questing/

there was no Release file because the PPA hasn't published packages for questing. Ubuntu therefore disables that repository for security reasons.

Do you need a PPA for htop?

No. htop is already in Ubuntu's official repositories, so a PPA isn't needed. The deadsnakes PPA is unrelated to htop; it just happened to cause apt update to fail before htop could be installed.

Should you use PPAs?

PPAs are common and can be useful, but it's generally a good idea to:

• Prefer Ubuntu's official repositories when they contain what you need.
• Add a PPA only when you specifically need software or versions that Ubuntu doesn't provide.
• Remove or disable PPAs you no longer use, especially after upgrading Ubuntu, because some PPAs lag behind new Ubuntu releases and can cause errors like the one you encountered.

 

Is it possible that the deadsnakes PPA will be available for ubuntu 25.10 later?

Yes, absolutely. In fact, that's fairly common.

A PPA is maintained independently by its owner. When a new Ubuntu release comes out, the maintainer has to:

1. Enable support for the new Ubuntu release (e.g. questing).
2. Build the packages against that release.
3. Publish them.

Until they do, users of the new release will see exactly the error you saw:

404 Not Found
... does not have a Release file

because there simply isn't a questing repository yet.

For popular PPAs like deadsnakes, support for new Ubuntu releases is often added, but there is no guarantee or fixed timeline. It depends on the maintainers' priorities and whether they decide to support that Ubuntu version.

In your case, you have a few options:

• If you don't need deadsnakes right now: remove or disable it. You can always add it back later if support for Ubuntu 25.10 becomes available.
• If you do need it: periodically check whether support has been added, then re-enable the repository and run sudo apt update.
• If you only wanted Python: Ubuntu 25.10 already includes a recent Python version, so you may not need deadsnakes at all.

One additional note: Ubuntu 25.10 is an interim release with a relatively short support period. If you don't specifically need the newest Ubuntu features, many people prefer using the latest LTS release because third-party PPAs and software vendors tend to support it sooner and for longer.

 

I disabled it for now: 

sudo mv /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-questing.sources \
        /etc/apt/sources.list.d/deadsnakes-ubuntu-ppa-questing.sources.disabled

This could be recovered later if needed.