Ubuntu installation instructions recommend a PPA unavailable for Ubuntu 26.04

The [Linux download page](https://haxe.org/download/linux/) recommends `ppa:haxe/releases` and states that it covers all currently supported Ubuntu versions. On Ubuntu 26.04 LTS (`resolute`), following the instructions:

```bash
sudo add-apt-repository ppa:haxe/releases -y
```

produces:

```text
E: The repository 'https://ppa.launchpadcontent.net/haxe/releases/ubuntu resolute Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
```

The repository entry is added despite the failure, so subsequent package-index updates also report the error until it is removed or disabled.

Meanwhile, [Ubuntu’s own repository](https://packages.ubuntu.com/resolute/haxe) provides Haxe 4.3.7, matching the stable version currently listed on the Haxe download page.

Could the Ubuntu instructions be updated to:

- Recommend Ubuntu’s package when its version is sufficiently recent.
- Make the PPA recommendation conditional on support for the user’s Ubuntu release, linking to its published packages.
- Explain how to remove the PPA if it was added on an unsupported release.

This would provide a working installation path even when PPA packages are unavailable for a newer Ubuntu release.

In general: Is Ubuntu 26.04 support planned for the PPA, or is there a compatibility or packaging constraint preventing it? In the meantime, would recommending Ubuntu’s own package be the preferred approach for this release?

Related: [haxe/issues/11210](https://github.com/HaxeFoundation/haxe/issues/11210) reported the same symptom for Ubuntu 22.10 in 2023. I’m opening this here because the proposed fix concerns the website’s installation instructions and fallback guidance for newer Ubuntu releases.

Start at the Linux download page linked in the issue and inspect the Ubuntu/PPA installation section in the website source. Done means the guidance offers Ubuntu’s package when suitable, conditions PPA use on published release support, and explains how to remove an unsupported PPA entry.

Written by the indexing model from the issue text.