SELinux is denying collectd from opening port 9103, which is used by the write_prometheus plugin.  Setting setenforce to 0 allows the collectd to use the port.  I added tcp/9103 to collectd_port_t and set the collectd_tcp_network_connect to "on".  Details below.

Mar 25 09:30:14 fedora41.example.com systemd[1]: Starting collectd.service - Collectd statistics daemon...
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "syslog" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "cpu" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "interface" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "load" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "memory" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_load: plugin "write_prometheus" successfully loaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: Systemd detected, trying to signal readiness.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: write_prometheus plugin: Opening a listening socket for [::]:9103 failed.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: Initialization of plugin `write_prometheus' failed with status -1. Plugin will be unloaded.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: plugin_unregister_read: No such read function: write_prometheus
Mar 25 09:30:14 fedora41.example.com collectd[1907]: Error: one or more plugin init callbacks failed.
Mar 25 09:30:14 fedora41.example.com collectd[1907]: Initialization complete, entering read-loop.
Mar 25 09:30:14 fedora41.example.com systemd[1]: Started collectd.service - Collectd statistics daemon.

# semanage port -l | grep collectd
collectd_port_t                tcp      9103
collectd_port_t                udp      25826

# getsebool collectd_tcp_network_connect
collectd_tcp_network_connect --> on

# sealert -l 0f8a6a8e-06d6-46d5-b0b3-73ffc10bbfd6
SELinux is preventing /usr/sbin/collectd from name_bind access on the tcp_socket port 9103.

*****  Plugin catchall (100. confidence) suggests   **************************

If you believe that collectd should be allowed name_bind access on the port 9103 tcp_socket by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# ausearch -c 'collectd' --raw | audit2allow -M my-collectd
# semodule -X 300 -i my-collectd.pp


Additional Information:
Source Context                system_u:system_r:collectd_t:s0
Target Context                system_u:object_r:collectd_port_t:s0
Target Objects                port 9103 [ tcp_socket ]
Source                        collectd
Source Path                   /usr/sbin/collectd
Port                          9103
Host                          fedora41.example.com
Source RPM Packages           collectd-5.12.0-44.fc41.x86_64
Target RPM Packages
SELinux Policy RPM            selinux-policy-targeted-41.34-1.fc41.noarch
Local Policy RPM              selinux-policy-targeted-41.34-1.fc41.noarch
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     fedora41.example.com
Platform                      Linux fedora41.example.com 6.13.8-200.fc41.x86_64 #1
                              SMP PREEMPT_DYNAMIC Sun Mar 23 05:03:09 UTC 2025
                              x86_64
Alert Count                   2
First Seen                    2025-03-25 09:30:14 EDT
Last Seen                     2025-03-25 09:30:14 EDT
Local ID                      0f8a6a8e-06d6-46d5-b0b3-73ffc10bbfd6

Raw Audit Messages
type=AVC msg=audit(1742909414.112:693): avc:  denied  { name_bind } for  pid=1907 comm="collectd" src=9103 scontext=system_u:system_r:collectd_t:s0 tcontext=system_u:object_r:collectd_port_t:s0 tclass=tcp_socket permissive=0


type=SYSCALL msg=audit(1742909414.112:693): arch=x86_64 syscall=bind success=no exit=EACCES a0=3 a1=55c8f9e52050 a2=10 a3=7fff70cfb694 items=0 ppid=1 pid=1907 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm=collectd exe=/usr/sbin/collectd subj=system_u:system_r:collectd_t:s0 key=(null)

Hash: collectd,collectd_t,collectd_port_t,tcp_socket,name_bind

Reproducible: Always

Steps to Reproduce:
1. dnf -y install collectd collectd-write_prometheus
2. cat << __EOF__ > /etc/collectd.d/write_prometheus.conf
LoadPlugin write_prometheus
<Plugin "write_prometheus">
  Port "9103"
</Plugin>
__EOF__
3. systemctl start collectd.service
Actual Results:  
Mar 25 09:30:14 fedora41.example.com collectd[1907]: write_prometheus plugin: Opening a listening socket for [::]:9103 failed.

Expected Results:  
Mar 25 08:59:55 fedora41.example.com collectd[1326354]: write_prometheus plugin: Listening on [::]:9103.