Upload via Android-App does not work with air-gapped instances?

### ⚠️ Before posting ⚠️

- [x] This is a **bug**, not a question or an enhancement.
- [x] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [x] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

Setup an air-gapped system: create a wifi setup which allows clients to connect only to selected internal services and make a nextcloud instance one of the few internal services accessible from within this wifi.

Using nextcloud via webbrowser on an android phone works fine.
Using nextcloud via android app does not really work.

### Expected behaviour

The app to not care about true internet connectivity if the instance is reachable.

### Actual behaviour

The app did not even try to upload any files, even when the NC-instance was reachable without any issues from the same device via webbrowser.

### Android version

16

### Device brand and model

Oneplus 8t

### Stock or custom OS?

Custom (explain in "additional information")

### Nextcloud android app version

3.34.1 (fdroid)

### Nextcloud server version

31.0.12

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

Current LineageOS 23.0