I wasn’t able to create or send messages as a normal user until I edited the policy in /usr/share/polkit-1/actions/org.freedesktop.ModemManager1.policy.
I removed the auth_admin value with a yes:
<allow_active>yes</allow_active>
That wasn’t sufficient, so I added this:
<allow_any>yes</allow_any>
A systemctl restart polkit was required after each change.
updated: 2022-12-07 23:18:13 -0500
generated: 2023-04-23