PostgreSQL 11 configurations doesn't allow pgAdmin4 to connect

Check SELinux audit logs - https://fedoraproject.org/wiki/SELinux_FAQ#How_do_I_find_out_whether_SELinux_is_denying_access_for_any_software.3F

I see denials on my test CentOS 7 system:

type=AVC msg=audit(1560101981.565:1942): avc:  denied  { name_connect } for  pid=63140 comm="httpd" dest=5432 scontext=system_u:system_r:httpd_t:s0 tcontext=system_u:object_r:postgresql_port_t:s0 tclass=tcp_socket permissive=0
type=SYSCALL msg=audit(1560101981.565:1942): arch=c000003e syscall=42 success=no exit=-13 a0=15 a1=7f741c06dfe0 a2=10 a3=7f742f9147b8 items=0 ppid=63139 pid=63140 auid=4294967295 uid=48 gid=48 euid=48 suid=48 fsuid=48 egid=48 sgid=48 fsgid=48 tty=(none) ses=4294967295 comm="httpd" exe="/usr/sbin/httpd" subj=system_u:system_r:httpd_t:s0 key=(null)

I guess, you will have similar problem in your Fedora - you will need to tweak used SELinux policy.