Btw you can also use normal third-party clients with your custom developer API key, there's a patched version of Apollo for iOS/iPadOS (you can download it from AltStore using their custom repository, it's explained on the website) and ReVanced offers a patch for Infinity on Android. The patched Apollo version has a quick guide on how to get an API Key, it works with all apps that support these custom keys though:
Sign into your Reddit account and go to the link above (reddit.com/prefs/apps)
Click the "are you a developer? create an app..." button
Fill in the fields
Name: anything
Choose "Installed App"
Description: anything
About url: anything
Redirect uri: apollo://reddit-oauth
Click "create app"
After creating the app you'll get a client identifier which will be a bunch of random characters.