I think the enable_auto_update option can be a little bit confusing.

What it does

Disable the "automatic update check".

Confusion

Does it disable the Update Automatically function in the Web UI or not.

Steps to reproduce

1. Setting enable_auto_update to 0
2. Update Automatically option is still available in the Web UI (CoreUpdater action newVersionAvailable)
3. Updating the instance is possible
4. After the successful update you'll receive an error: An error occurred: Auto updater is disabled

Expected behavior

After setting enable_auto_update to 0 updates over the Web UI aren't possible any more.

Cheer @vrandr technically, it was kind of already working because when disabled, Matomo would no longer look if an update is available. The method you mentioned would still work though if at the time of disabling a newer version was available. Added https://github.com/matomo-org/matomo/pull/17105 for now.

I think #17106 is the correct linked issue.