Hi there! I understand you're having trouble finding the login option after deleting and reinstalling the Substack app on your Mac running OS X 10.15.7. Just to clarify, when you reopen the app after reinstalling, do you see any screen at all—like a welcome page, create account, or anything else—or does it jump straight to something else, like a new subscription screen or something? Also, have you tried any steps so far to fix this?

Once I have a bit more detail, I can guide you through some steps to get you logged back in. Meanwhile, here are some general troubleshooting tips that might help:

1. Check for App Updates: Make sure you have the latest version of the Substack app installed from the official source.

2. Restart Your Device: Sometimes a quick restart of your Mac refreshes system processes related to the app.

3. Clear Cache or Data: On macOS apps, this is less straightforward, but reinstalling the app usually clears cache. Since you've reinstalled, this is covered.

4. Look for Login via Email: Substack uses magic links sent by email to sign you in, rather than passwords traditionally. After you open the app, it sometimes sends you a login email automatically, or you may need to request one through the app. If you don’t see a login button, try visiting Substack's website on your browser and requesting a login link sent to your email, then tap that link on your Mac to authenticate the app.

5. Check Email Spam/Junk Folder: Make sure the login email isn't filtered.

6. No Login Option: Some users report that after reinstalling, the app may only show the option to create a new account initially, which is confusing. In that case, you can try to tap "Create Account" and look carefully for a "Log In" link or button on that screen—it is sometimes hidden or less prominent.

Please let me know what you see when you open the app, and if you've tried any of these steps, so I can assist you further!