So i’m on strike and so i got a moment to continue investigations…
I find a “solution”…
i describe it here 
https://forum.yunohost.org/t/invalid-token-as-suggest-by-lychee-team-maybe-its-a-yunohost-issue/23950/5
Hello,
i find a solution and it was to put in
nano /var/www/lychee/.env
ENABLE_TOKEN_AUTH=true
i also enable debug…
There is still a problem in managing the token in yunohost…
as it is advice on this page:
Lychee Documentation
i restart the server and it seems to work…
and now i’m in lychee… Youhou !
i put the diagnostic log here because it could be helpfull…
Diagnostics
-------
Warning: /home/yunohost.app/lychee/uploads/ is owned by group www-data, but should be owned by one out of lychee
Warning: /home/yunohost.app/lychee/uploads/ has permissions 0770, but should have 2775
Warning: /home/yunohost.app/lychee/uploads/small is owned by group www-data, but should be owned by one out of lychee
Warning: /home/yunohost.app/lychee/uploads/small has permissions 0770, but should have 2775
Warning: /home/yunohost.app/lychee/uploads/raw is owned by group www-data, but should be owned by one out of lychee
Warning: /home/yunohost.app/lychee/uploads/raw has permissions 0770, but should have 2775
Warning: /home/yunohost.app/lychee/uploads/import is owned by group www-data, but should be owned by one out of lychee
Warning: /home/yunohost.app/lychee/uploads/import has permissions 0770, but should have 2775
Warning: /home/yunohost.app/lychee/uploads/big is owned by group www-data, but should be owned by one out of lychee
Warning: /home/yunohost.app/lychee/uploads/big has permissions 0770, but should have 2775
Warning: 3 more directories with wrong owner
Warning: 3 more directories with wrong permissions
Warning: Dropbox import not working. dropbox_key is empty.
Warning: You may experience problems when uploading a photo of large size or handling many/large albums. Take a look in the FAQ for details.
Warning: zend.assertions is disabled although Lychee is in debug mode. For easier debugging code generation for assertions should be enabled.
Info: Latest version of PHP is 8.2
Warning: Default timezone not properly set; you might experience strange results when importing photos without explicit EXIF timezone
System Information
--------------
Lychee Version (release): 4.7.0
DB Version: 4.7.0
composer install: --no-dev
APP_ENV: production
APP_DEBUG: true
System: Linux
PHP Version: 8.1.16
PHP User agent: Lychee/4 (https://lycheeorg.github.io/)
Timezone: UTC
Max uploaded file size: 512M
Max post size: 512M
Max execution time: 30
MySQL Version: 10.5.18-MariaDB-0+deb11u1
exec() Available: yes
Imagick Available: 1
Imagick Enabled: 1
Imagick Version: 1691
GD Version: 2.3.3
Number of foreign key: 11 found.
Config Information
--------------
version: 040700
check_for_updates: 0
sorting_photos_col: taken_at
sorting_photos_order: ASC
sorting_albums_col: max_taken_at
sorting_albums_order: ASC
imagick: 1
skip_duplicates: 0
small_max_width: 0
small_max_height: 360
medium_max_width: 1920
medium_max_height: 1080
lang: en
layout: 1
image_overlay_type: desc
default_license: none
compression_quality: 90
grants_full_photo_access: 1
delete_imported: 0
mod_frame_enabled: 1
mod_frame_refresh: 30
thumb_2x: 1
small_2x: 1
medium_2x: 1
landing_page_enable: 0
site_owner: John Smith
landing_title: John Smith
landing_subtitle: Cats, Dogs & Humans Photography
sm_facebook_url: https://www.facebook.com/JohnSmith
sm_flickr_url: https://www.flickr.com/JohnSmith
sm_twitter_url: https://www.twitter.com/JohnSmith
sm_instagram_url: https://instagram.com/JohnSmith
sm_youtube_url: https://www.youtube.com/JohnSmith
landing_background: dist/cat.webp
site_title: Lychee v4
footer_show_copyright: 1
site_copyright_begin: 2019
site_copyright_end: 2019
footer_additional_text:
footer_show_social_media: 0
public_search: 0
SL_enable: 0
SL_for_admin: 0
public_recent: 0
recent_age: 1
public_starred: 0
grants_download: 0
photos_wraparound: 1
map_display: 0
zip64: 1
map_display_public: 0
map_provider: Wikimedia
force_32bit_ids: 0
map_include_subalbums: 0
update_check_every_days: 3
has_exiftool: 1
share_button_visible: 0
import_via_symlink: 0
has_ffmpeg: 1
location_decoding: 0
location_decoding_timeout: 30
location_show: 1
location_show_public: 0
rss_enable: 0
rss_recent_days: 7
rss_max_items: 100
prefer_available_xmp_metadata: 0
editor_enabled: 1
lossless_optimization: 0
swipe_tolerance_x: 150
swipe_tolerance_y: 250
local_takestamp_video_formats: .avi|.mov
log_max_num_line: 1000
unlock_password_photos_with_url_param: 0
nsfw_visible: 1
nsfw_blur: 0
nsfw_warning: 0
nsfw_warning_admin: 0
nsfw_banner_override:
map_display_direction: 1
album_subtitle_type: oldstyle
upload_processing_limit: 4
public_photos_hidden: 1
new_photos_notification: 0
legacy_id_redirection: 1
zip_deflate_level: 6
SA_enabled: 1
default_album_protection: 1
album_decoration: layers
album_decoration_orientation: row
allow_username_change: 1
thanks