I want to PERMANENTLY run my iPhone on SILENT for all incoming calls. But no setting seems to exist to enable this.

Option 1 (allows calls but makes no indication that they have arrived, so you won’t know you are receiving a call unless you are watching the screen):

• Buy or create a silent ringtone.
• Install it on your phone.
• Go to Settings/Sounds & Haptics.
• Select the silent ringtone.

Option 2 (Sends all calls to voicemail):

• Go to Settings/Focus
• Tap on Do Not Disturb
• Tap on People
• Tap Allow Notifications From
• Make sure there are no people listed; thus, “Allow Notifications From No One"
• Tap on the Allow Calls From dropdown and choose Allowed People Only
• Turn off Allow Repeated Calls

EITHER:

• Tap on Back
• Tap on Add Schedule
• Create a schedule that runs for 24 hours every day

OR:

• Open the Control Center by dragging down from the Battery icon
• Tap Focus so it reads Do Not Disturb