Yes, essentially. I do have the Guardian Project repository and I get a handful of applications from the Play Store (via Aurora Store), but everything else comes from F-Droid. If you want even more, you can add the IzzyOnDroid repository[0], but bear in mind that unlike F-Droid, applications are built by developers themselves, and the rules on FOSS-only licensing are less strict.

[0]: https://apt.izzysoft.de/fdroid/