There is no help for the Remote Files dialog (File - Open Remote File - Help).
Hello Stanislav, *, I can confirm it with OS: Debian Testing AMD64 LO: Version: 5.1.5.1 Build-ID: 1:5.1.5~rc1-1 CPU-Threads: 4; BS-Version: Linux 4.5; UI-Render: GL; Gebietsschema: de-DE (de_DE.UTF-8); Calc: group (Debian's own version) and LO: Version: 5.2.0.3 Build ID: 7dbd85f5a18cfeaf6801c594fc43a5edadc2df0c CPU Threads: 4; OS Version: Linux 4.5; UI Render: default; Locale: de-DE (de_DE.UTF-8) (parallel installed, following the instructions from https://wiki.documentfoundation.org/Installing_in_parallel/Linux) ... :( Setting the status to "New" and changing the version to 5.1.5.1, as this is the older version ... ;) If someone else would be so kind to test older versions and change the version to his/her found older version, that would be really nice ... ;) HTH Thomas.
*** This bug has been marked as a duplicate of bug 80652 ***