Hi !
This might be true to the root user but icinga should use its own user account which is icinga. Also beside that SIP under Big Sur prevents for security reasons almost all non system accounts in writing in system directories like /var/log.
This might not be a “cool” or secure suggestion but could you disable the SIP and also take a look into the “security & privacy” tab of the system preferences if there shows up an allowance question ?
Regards
David
