Can't access files in Linux (dolphin + dav) and maybe Android

Nextcloud version (eg, 20.0.5): 20.0.8
Operating system and version (eg, Ubuntu 20.04): Linux
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4.46
PHP version (eg, 7.4): 7.4.14

The issue you are facing:
I can’t access my files in Linux.
I also can’t see them in my Android phone’s file manager, whereas I can see Google Drive there (not sure if this is an error).
However, I can see them via web browser, and in the Nextcloud Android app.

For a long time I didn’t even realized I was missing anything, but something didn’t feel right.
At this point I’m not even sure what I’m missing.

I configured Dolphin to access Nextcloud using KDE’s “System Settings” → “Online Accounts”.
When I try to access it in Dolphin, it goes to:
webdavs://username@cloud.domain.com/remote.php/dav/files/username/

This doesn’t show any error message, but it’s empty.
In Apache I get these log entries:

2021-03-10T11:20:13+09:00 cloud.example.com 10.6.0.110 TLSv1.3 "PROPFIND /remote.php/dav/files/username HTTP/1.1" 404 226 "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/534.34 (KHTML, like Gecko) dolphin/20.12.3 Safari/534.3"
2021-03-10T11:20:13+09:00 cloud.example.com 10.6.0.110 TLSv1.3 "PROPFIND /remote.php/dav/files/username HTTP/1.1" 404 226 "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/534.34 (KHTML, like Gecko) dolphin/20.12.3 Safari/534.3"
2021-03-10T11:20:13+09:00 cloud.example.com 10.6.0.110 TLSv1.3 "PROPFIND /remote.php/dav/files/username/ HTTP/1.1" 404 226 "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/534.34 (KHTML, like Gecko) dolphin/20.12.3 Safari/534."

However, when I access it from the Nextcloud app, I get these:

2021-03-10T11:24:02+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /index.php/204 HTTP/1.1" 204 - "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:02+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /index.php/204 HTTP/1.1" 204 - "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:08+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v1.php/cloud/user?format=json HTTP/1.1" 200 595 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:08+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /status.php HTTP/1.1" 200 174 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /status.php HTTP/1.1" 200 174 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v2.php/cloud/capabilities?format=json HTTP/1.1" 304 - "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v2.php/cloud/capabilities?format=json HTTP/1.1" 304 - "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.2 "GET /ocs/v2.php/apps/user_status/api/v1/predefined_statuses?format=json HTTP/1.1" 200 259 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.2 "GET /ocs/v2.php/apps/user_status/api/v1/predefined_statuses?format=json HTTP/1.1" 200 259 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v1.php/cloud/user?format=json HTTP/1.1" 200 595 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v1.php/cloud/user?format=json HTTP/1.1" 200 595 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "PROPFIND /remote.php/webdav/ HTTP/1.1" 207 814 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:09+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "PROPFIND /remote.php/webdav/ HTTP/1.1" 207 814 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:10+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "PROPFIND /remote.php/webdav/ HTTP/1.1" 207 6124 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:10+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "PROPFIND /remote.php/webdav/ HTTP/1.1" 207 6124 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:11+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v2.php/apps/files_sharing/api/v1/shares?path=%2F&reshares=true&subfiles=true HTTP/1.1" 200 3588 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"
2021-03-10T11:24:11+09:00 cloud.example.com 10.6.0.130 TLSv1.3 "GET /ocs/v2.php/apps/files_sharing/api/v1/shares?path=%2F&reshares=true&subfiles=true HTTP/1.1" 200 3588 "Mozilla/5.0 (Android) Nextcloud-android/3.15.0" "-"

Two things I noticed:

  1. The URLs are different
  2. The Nextcloud app works, but requests are duplicated. Is that normal?

I’m omitting the Nextcloud debug logs because they don’t seem to have anything useful, and because they are in JSON format.
My Nextcloud config doesn’t have anything special either, except that I configured my users via LDAP, but I don’t think that’s relevant.

Thanks in advance to anyone who can answer my questions.