Update Ubuntu/Debian install instructions

[michaelblyons]

Problem description

Debian (and by extension, Ubuntu) are moving to a new format for installing new .deb sources, such that keyrings from extra sources aren't inadvertently used to overwrite packages from other providers.

Preferred solution

Update the apt installation instructions. This replacement block has been mooted on Discord in #general by mrp on 2025-04-20:

sudo curl -fsSL https://download.sublimetext.com/sublimehq-pub.gpg -o /etc/apt/keyrings/sublimehq-pub.asc

cat << EOF | sudo tee /etc/apt/sources.list.d/sublime-text.sources
Types: deb
URIs: https://download.sublimetext.com/
Suites: apt/stable/
Components:
Signed-By: /etc/apt/keyrings/sublimehq-pub.asc
EOF

Alternatives

You could add a [signed-by=...] section into the deb line in the old format to prevent other keys from asserting control over your packages.

Additional Information

The new sources format is the default in Ubuntu 25.04, and will be in Debian 13 as well. Debian 12 (current stable until later this year) supports it, too.

[gouenji-shuuya]

Please use the deb822 format now. Everything would stay in one file. I use it and it's working fine.

[BenjaminSchaaf]

Fixed in build 4199.