Release checklist

Run build-scripts/create-release.py -R libsdl-org/SDL --ref <git-ref> to command GitHub Actions to start creating release assets. It's advisable to run this script regularly, and also prior to any release step. When creating the release assets, <git-ref> must be the release tag This makes sure the revision string baked into the archives is correct.
When changing the version, run build-scripts/update-version.sh X Y Z, where X Y Z are the major version, minor version, and patch level. So 3 8 1 means "change the version to 3.8.1". This script does much of the mechanical work.

New feature release

Check that no new API/ABI was added
- If it was, do a new feature release (see above) instead
Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is even)
- ./build-scripts/update-version.sh 3 Y Z+1
Do the release
Update the website file include/header.inc.php to reflect the new version

Create a branch like release-3.4.x
Bump version number to 3.ODD.0 for next development branch
- ./build-scripts/update-version.sh 3 ODD 0

Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is odd)
- ./build-scripts/update-version.sh 3 Y Z+1
Do the release