root@turris:~# cat /etc/cron.d/rainbow
MAILTO=""
0 18 * * * root /usr/bin/rainbow intensity 5
0 8 * * * root /usr/bin/rainbow intensity 100
root@turris:~# /usr/bin/rainbow intensity 5
Command failed: Not found
Command failed: Not found
Today was released new version TurrisOS (6.4.0) with new version of rainbow package.
Maybe it helps you …
https://forum.turris.cz/t/turris-os-6-4-0-is-released-now/19169