Limit connections to specific port

How to limit the number of Connections to a specific port. Example 6 connections per 100 /s

The nftables seems to have limit rate and ct count features: Meters - nftables wiki

Whether you implement your ruleset with firewalld.service or nftables.service is up to you. See Configuring firewalls and packet filters Red Hat Enterprise Linux 9 | Red Hat Customer Portal