AUCTeX/Evince: server does not start, poor direct search, inverse search does not work

[Cédric M. Campos]

Ubuntu release: Ubuntu 18.04.2 LTS (fully updated as per today)
Package version: AUCTeX 11.91 (Emacs 25.2)

*** Summary ***
1) Evince server does not start, so each "C-c C-v" issued opens a new Evince instance, capturing the keyboard focus and bloating the screen.
2) Direct search works partially, it merely searches for the page and not the specific line.
3) Inverse search simply does not work.

*** Note ***
I have attached a basic configuration to start a server and activate direct/inverse search according to this: https://www.gnu.org/software/auctex/manual/auctex/I_002fO-Correlation.html

*** What is to be expected ***
1) Open a .tex file with Emacs/AUCTeX.
2) Compile (C-c C-c).
3) View pdf output (C-c C-v).
>> An Evince server for that file is started.
>> Evince opens the pdf file.
>> Focus is still on Emacs instance.
3) Move to some line (in Emacs).
4) View pdf output (C-c C-v).
>> No new Evince instance is opened for that file.
>> The current Evince instance moves to the specific line corresponding to the cursor position in Emacs.
>> Focus is still on Emacs instance.
5) On Evince "control+left click" some line.
>> Emacs moves to the specific line corresponding to the pointed line in Evince.
>> Emacs instance captures the focus.

*** What happens ***
1) Open a .tex file with Emacs/AUCTeX.
2) Compile (C-c C-c).
3) View pdf output (C-c C-v).
>> No Evince server is started.
>> Evince opens the pdf file.
>> Focus is captured by Evince.
3) Move to some line (in Emacs).
4) View pdf output (C-c C-v).
>> A new Evince instance is opened for that file.
>> The new Evince instance moves to the page (not the line) corresponding to the cursor position in Emacs.
>> Focus is captured by the new Evince instance.
5) On Evince "control+left click" some line.
>> Nothing happens and Winter Is Coming.

[Cédric M. Campos (cedricmc)]

SOLVED. Some non-official package installed Evince through flatpak, which did not communicate properly with AUCTeX through D-Bus.