As of iOS 13.1, these URLs are back, and have been exhaustively documented on the MacStories website by Federico Viticci. Please note that the linked page is being actively updated, and contains other useful background and tips such as how to link to the settings for third party apps, so probably a good idea to follow the linke through to that site for the full info:

Settings URLs iCloud

iCloud: prefs:root=CASTLE
iCloud Backup: prefs:root=CASTLE&path=BACKUP

Wireless Radios

Wi-Fi: prefs:root=WIFI
Bluetooth: prefs:root=Bluetooth
Cellular: prefs:root=MOBILE_DATA_SETTINGS_ID

Personal Hotspot

Personal Hotspot: prefs:root=INTERNET_TETHERING
Personal Hotspot ⇾ Family Sharing: prefs:root=INTERNET_TETHERING&path=Family%20Sharing
Personal Hotspot ⇾ Wi-Fi Password: prefs:root=INTERNET_TETHERING&path=Wi-Fi%20Password

VPN

VPN: prefs:root=General&path=VPN

Notifications

Notifications: prefs:root=NOTIFICATIONS_ID
Notifications ⇾ Siri Suggestions: prefs:root=NOTIFICATIONS_ID&path=Siri%20Suggestions

Sounds

Sounds: prefs:root=Sounds
Ringtone: prefs:root=Sounds&path=Ringtone

Do Not Disturb

Do Not Disturb: prefs:root=DO_NOT_DISTURB
Do Not Disturb ⇾ Allow Calls From: prefs:root=DO_NOT_DISTURB&path=Allow%20Calls%20From

Screen Time

Screen Time: prefs:root=SCREEN_TIME
Screen Time ⇾ Downtime: prefs:root=SCREEN_TIME&path=DOWNTIME
Screen Time ⇾ App Limits: prefs:root=SCREEN_TIME&path=APP_LIMITS
Screen Time ⇾ Always Allowed: prefs:root=SCREEN_TIME&path=ALWAYS_ALLOWED

General

General: prefs:root=General
General ⇾ About: prefs:root=General&path=About
General ⇾ Software Update: prefs:root=General&path=SOFTWARE_UPDATE_LINK
General ⇾ CarPlay: prefs:root=General&path=CARPLAY
General ⇾ Background App Refresh: prefs:root=General&path=AUTO_CONTENT_DOWNLOAD
General ⇾ Multitasking (iPad-only): prefs:root=General&path=MULTITASKING
General ⇾ Date & Time: prefs:root=General&path=DATE_AND_TIME
General ⇾ Keyboard: prefs:root=General&path=Keyboard
General ⇾ Keyboard ⇾ Keyboards: prefs:root=General&path=Keyboard/KEYBOARDS
General ⇾ Language & Region: prefs:root=General&path=INTERNATIONAL
General ⇾ Dictionary: prefs:root=General&path=DICTIONARY
General ⇾ Profiles: prefs:root=General&path=ManagedConfigurationList
General ⇾ Reset: prefs:root=General&path=Reset

Control Center

Control Center: prefs:root=ControlCenter
Control Center ⇾ Customize Controls: prefs:root=ControlCenter&path=CUSTOMIZE_CONTROLS

Display

Display: prefs:root=DISPLAY
Display ⇾ Auto Lock: prefs:root=DISPLAY&path=AUTOLOCK
Display ⇾ Text Size: prefs:root=DISPLAY&path=TEXT_SIZE

Accessibility

Accessibility: prefs:root=ACCESSIBILITY

Wallpaper

Wallpaper: prefs:root=Wallpaper

Siri

Siri: prefs:root=SIRI

Apple Pencil

Apple Pencil (iPad-only): prefs:root=Pencil

Face ID

Face ID: prefs:root=PASSCODE

Emergency SOS

Emergency SOS: prefs:root=EMERGENCY_SOS

Battery

Battery: prefs:root=BATTERY_USAGE
Battery ⇾ Battery Health (iPhone-only): prefs:root=BATTERY_USAGE&path=BATTERY_HEALTH

Privacy

Privacy: prefs:root=Privacy
Privacy ⇾ Location Services: prefs:root=Privacy&path=LOCATION
Privacy ⇾ Contacts: prefs:root=Privacy&path=CONTACTS
Privacy ⇾ Calendars: prefs:root=Privacy&path=CALENDARS
Privacy ⇾ Reminders: prefs:root=Privacy&path=REMINDERS
Privacy ⇾ Photos: prefs:root=Privacy&path=PHOTOS
Privacy ⇾ Microphone: prefs:root=Privacy&path=MICROPHONE
Privacy ⇾ Speech Recognition: prefs:root=Privacy&path=SPEECH_RECOGNITION
Privacy ⇾ Camera: prefs:root=Privacy&path=CAMERA
Privacy ⇾ Motion: prefs:root=Privacy&path=MOTION\

App Store

App Store: prefs:root=STORE
App Store ⇾ App Downloads: prefs:root=STORE&path=App%20Downloads
App Store ⇾ Video Autoplay: prefs:root=STORE&path=Video%20Autoplay

Wallet

Wallet: prefs:root=PASSBOOK

Passwords & Accounts

Passwords & Accounts: prefs:root=ACCOUNTS_AND_PASSWORDS
Passwords & Accounts ⇾ Fetch New Data: prefs:root=ACCOUNTS_AND_PASSWORDS&path=FETCH_NEW_DATA
Passwords & Accounts ⇾ Add Account: prefs:root=ACCOUNTS_AND_PASSWORDS&path=ADD_ACCOUNT

Mail

Mail: prefs:root=MAIL
Mail ⇾ Preview: prefs:root=MAIL&path=Preview
Mail ⇾ Swipe Options: prefs:root=MAIL&path=Swipe%20Options
Mail ⇾ Notifications: prefs:root=MAIL&path=NOTIFICATIONS
Mail ⇾ Blocked: prefs:root=MAIL&path=Blocked
Mail ⇾ Muted Thread Action: prefs:root=MAIL&path=Muted%20Thread%20Action
Mail ⇾ Blocked Sender Options: prefs:root=MAIL&path=Blocked%20Sender%20Options
Mail ⇾ Mark Addresses: prefs:root=MAIL&path=Mark%20Addresses
Mail ⇾ Increase Quote Level: prefs:root=MAIL&path=Increase%20Quote%20Level
Mail ⇾ Include Attachments with Replies: prefs:root=MAIL&path=Include%20Attachments%20with%20Replies
Mail ⇾ Signature: prefs:root=MAIL&path=Signature
Mail ⇾ Default Account: prefs:root=MAIL&path=Default%20Account

Contacts

Contacts: prefs:root=CONTACTS

Calendar

Calendar: prefs:root=CALENDAR
Calendar ⇾ Alternate Calendars: prefs:root=CALENDAR&path=Alternate%20Calendars
Calendar ⇾ Sync: prefs:root=CALENDAR&path=Sync
Calendar ⇾ Default Alert Times: prefs:root=CALENDAR&path=Default%20Alert%20Times
Calendar ⇾ Default Calendar: prefs:root=CALENDAR&path=Default%20Calendar

Notes

Notes: prefs:root=NOTES
Notes ⇾ Default Account: prefs:root=NOTES&path=Default%20Account
Notes ⇾ Password: prefs:root=NOTES&path=Password
Notes ⇾ Sort Notes By: prefs:root=NOTES&path=Sort%20Notes%20By
Notes ⇾ New Notes Start With: prefs:root=NOTES&path=New%20Notes%20Start%20With
Notes ⇾ Sort Checked Items: prefs:root=NOTES&path=Sort%20Checked%20Items
Notes ⇾ Lines & Grids: prefs:root=NOTES&path=Lines%20%26%20Grids
Notes ⇾ Access Notes from Lock Screen: prefs:root=NOTES&path=Access%20Notes%20from%20Lock%20Screen

Reminders

Reminders: prefs:root=REMINDERS
Reminders ⇾ Default List: prefs:root=REMINDERS&path=DEFAULT_LIST

Voice Memos

Voice Memos: prefs:root=VOICE_MEMOS

Phone

Phone: prefs:root=Phone

Messages

Messages: prefs:root=MESSAGES

FaceTime

FaceTime: prefs:root=FACETIME

Maps

Maps: prefs:root=MAPS
Maps ⇾ Driving & Navigation: prefs:root=MAPS&path=Driving%20%26%20Navigation
Maps ⇾ Transit: prefs:root=MAPS&path=Transit

Compass

Compass: prefs:root=COMPASS

Measure

Measure: prefs:root=MEASURE

Safari

Safari: prefs:root=SAFARI
Safari ⇾ Content Blockers: prefs:root=SAFARI&path=Content%20Blockers
Safari ⇾ Downloads: prefs:root=SAFARI&path=DOWNLOADS
Safari ⇾ Close Tabs: prefs:root=SAFARI&path=Close%20Tabs
Safari ⇾ Page Zoom: prefs:root=SAFARI&path=Page%20Zoom
Safari ⇾ Request Desktop Website: prefs:root=SAFARI&path=Request%20Desktop%20Website
Safari ⇾ Reader: prefs:root=SAFARI&path=Reader
Safari ⇾ Camera: prefs:root=SAFARI&path=Camera
Safari ⇾ Microphone: prefs:root=SAFARI&path=Microphone
Safari ⇾ Location: prefs:root=SAFARI&path=Location

News

News: prefs:root=NEWS

Health

Health: prefs:root=HEALTH

Shortcuts

Shortcuts: prefs:root=SHORTCUTS

Music

Music: prefs:root=MUSIC
Music ⇾ Cellular Data: prefs:root=MUSIC&path=com.apple.Music:CellularData
Music ⇾ Optimize Storage: prefs:root=MUSIC&path=com.apple.Music:OptimizeStorage
Music ⇾ EQ: prefs:root=MUSIC&path=com.apple.Music:EQ
Music ⇾ Volume Limit: prefs:root=MUSIC&path=com.apple.Music:VolumeLimit

Photos

Photos: prefs:root=Photos

Camera

Camera: prefs:root=CAMERA
Camera ⇾ Record Video: prefs:root=CAMERA&path=Record%20Video
Camera ⇾ Record Slo-mo: prefs:root=CAMERA&path=Record%20Slo-mo

Books

Books: prefs:root=IBOOKS

Game Center

Game Center: prefs:root=GAMECENTER