If I understand correctly, you're interested in using GOS without relying on an app store? If so you can transfer an APK using a USB-C to USB-C connection, an external storage device, or Bluetooth.
If that's not the case, you can utilize Vanadium to access F-Droid. However, please note that F-Droid utilizes an outdated software toolkit (STK). As an alternative, I would recommend downloading Droid-ify instead.
For my GOS device, I prefer to keep a minimal setup with just 20 apps, that number includes the default ones.