Yes, both Nagios XI and Zenduty offer a Free Trial.
Nagios XI is designed for Large Enterprises, Medium Business and Small Business.
Zenduty is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
The starting price of Zenduty begins at $5/User/Month when Billed Yearly, while pricing details for Nagios XI are unavailable.
Some top alternatives to Nagios XI includes Zabbix, Ne.Mo. Network Monitoring, PRTG Network Monitor, Spiceworks Network Monitor, Nagios Network Analyzer, SolarWinds ipMonitor, Netcrunch, OP5 Monitor, SolarWinds Network Performance Monitor, Checkmk and NinjaOne (NinjaRMM).
Some top alternatives to Zenduty includes Freshservice, PagerDuty, Opsgenie, VictorOps, AlertOps, Spike.sh, Rootly, Incident.io, StatusCast Incident Management, PagerTree and ResQ.