I discovered this (see below) leading me to think that some probe that worked in 5.5 no longer works in 5.8; so the whole monitoring engine can't run now? Or are these unconfigured objects that won't let the monitoring engine run?
[root@campusmon2v2 ~]# systemctl status nagios.service
● nagios.service - Nagios Core 4.4.6
Loaded: loaded (/usr/lib/systemd/system/nagios.service; enabled; vendor preset: disabled)
Active: failed (Result: signal) since Wed 2021-05-26 10:52:07 CDT; 38min ago
Docs:
https://www.nagios.org/documentation
Process: 9244 ExecStopPost=/bin/rm -f /usr/local/nagios/var/rw/nagios.cmd (code=exited, status=0/SUCCESS)
Process: 8702 ExecStart=/usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg (code=exited, status=0/SUCCESS)
Process: 8677 ExecStartPre=/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg (code=exited, status=0/SUCCESS)
Main PID: 8705 (code=killed, signal=ABRT)
May 26 10:51:26 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'NSClient Health via ACES-NAGIOS' on host 'ace-ts-db'. Unable to find service
May 26 10:51:26 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'NSClient Version via ACES-NAGIOS' on host 'aces-dfs-h1'. Unable to find service
May 26 10:51:26 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'via ACES-NAGIOS' on host 'abe-web'. Unable to find service
May 26 10:51:26 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'NSClient Version via ACES-NAGIOS' on host 'ansci-p10r87407'. Unable t...nd service
May 26 10:51:35 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'NSClient Version via ACES-NAGIOS' on host 'aces-dfs-3t'. Unable to find service
May 26 10:51:43 campusmon2v2.techservices.illinois.edu nagios[8705]: Error: Got check result for service 'Uptime via ACES-NAGIOS' on host 'abe-web'. Unable to find service
May 26 10:52:07 campusmon2v2.techservices.illinois.edu systemd[1]: nagios.service: main process exited, code=killed, status=6/ABRT
May 26 10:52:07 campusmon2v2.techservices.illinois.edu nagios[8765]: Caught SIGTERM, shutting down...
May 26 10:52:07 campusmon2v2.techservices.illinois.edu systemd[1]: Unit nagios.service entered failed state.
May 26 10:52:07 campusmon2v2.techservices.illinois.edu systemd[1]: nagios.service failed.
Hint: Some lines were ellipsized, use -l to show in full.