Got it to work. Followed the instructions from here:
https://www.idropnews.com/how-to/st...t-heres-how-you-can-try-and-enable-it/127831/
Numerous users have reported success with switching accounts and getting dark mode enabled, and we’ve tested this ourselves and it works — again, provided you have access to an account that has already been enabled for dark mode. The trick is to make sure that the “dark mode” account is the only one enabled on your device when launching the app.
- Open the Gmail app on your iPhone or iPad
- Tap on your picture in the top-right corner to bring up your list of accounts.
- Tap Manage accounts on this device.
- Switch off all of your accounts except for one.
- Tap Done.
- Force-quit the Gmail app.
- Wait about five seconds to make sure the app is fully closed.
- Enable Dark Mode on your iPhone or iPad if it’s not already.
- Launch the Gmail app.
If the selected account has been enabled for Gmail’s new dark mode, the app should launch in dark mode. If not, repeat the above steps with a different account selected. If dark mode hasn’t yet been enabled for any of your accounts, and you’re desperate to have it, some users have also reported success getting it by setting up a new Gmail account.