GitHub has 'OAuth Apps' and 'GitHub Apps' [0]. The former's scopes do not permit such granularity (eg the `repo` scope gives access to all repos of the account [1]).
The latter is much more granular, allowing the user to select specific repos to grant permission [2]. The 'GitHub App' owner can see their installations and also determine if the user chose access for all repos or on a per repo basis.
Netlify does such granular installation and will prompt you if you don't see your repo listed in their dashboard to check permissions.
[0] https://docs.github.com/en/developers/apps/getting-started-w...
[1] https://docs.github.com/en/developers/apps/building-oauth-ap...
[2] https://docs.github.com/en/developers/apps/managing-github-a...