Are there any simple ways to get natural sounding text-to-speech on Linux?

[xopi]

Install festival:
Select distro in https://pkgs.org/search/?q=festival
E.g. for Ubuntu 20.04 https://ubuntu.pkgs.org/20.04/ubuntu...arm64.deb.html
In there search for: Install Howto and run it:

    # Update the package index:
    sudo apt-get update
    # Install festival deb package:
    sudo apt-get install festival

If desired to install through binaries, you may check:
https://www.cstr.ed.ac.uk/projects/f.../download.html
http://www.festvox.org/docs/manual-2...l#Installation
https://wiki.ubuntuusers.de/Festival/
https://wiki.ubuntuusers.de/Festival/Kompilieren/ --> to use german voices

Partial outdated guide to add further voices: https://ubuntuforums.org/showthread....light=festival (19 pages long thread! )
E.g. use CMU Arctic voices
Its section "Installing the enhanced CMU Arctic voices" should be corrected [but it's closed thread] (rest of steps works for me in Ubuntu 20.04):

sudo mv * /usr/share/festival/voices/us/

instead of

sudo mv * /usr/share/festival/voices/english/ # WRONG

Also specified in its README file:

$ batcat [path_to_unzip_CMU_Arctic_voice]/README
   1   │ 
   2   │ CMU ARCTIC AWB 0.90
   3   │ 
   4   │ This distrory contains a recording of the phonetically balanced US
   5   │ English CMU ARCTIC database by AWB, a Scottish English speaker.
...
  53   │ INSTALLING AS A FESTIVAL VOICE
  54   │ ==============================
...
  73   │ Or to install as voice in your Festival installation it must appear
  74   │ as a subdirectory of a subdirectory of a directory listed in the 
  75   │ Festival variable voice-path.  For standard installations you can
  76   │ create the following directory if it doesn't exist
  77   │ 
  78   │     /...WHATEVER.../festival/lib/voices/us/

Online test voices: http://festvox.org/voicedemos.html
And the whole list of voices can be checked in: http://www.speech.cs.cmu.edu/cmu_arctic/packed/

[QIII]

Good night, sweet thread.

Requiescat in pace.