For MX21 and MX23 :
https://repology.org/project/fotowall/versions
The useful Fotowall app. is available as a stand alone amd64 exe.
https://github.com/enricoros/fotowall/releases/tag/v1.0
Fotowall-1.0-RETRO-Linux_static-x86_64.x86_64

==== For info, was avalaible into MX 19 ================
viewtopic.php?p=545846&hilit=fotowall#p545846
MX19 - Request Fotowall
Hello,
Request to add Fotowall (for MX19 too)
...And additional frames:
https://blog.subsole.net/cadres-supplem ... -fotowall/
Additional frames for Fotowall (Cadres supplémentaires pour Fotowall)
https://www.enricoros.com/opensource/fotowall/
Image
https://www.enricoros.com/opensource/fo ... Abioqa.jpg