Logging out/in doesn't solve, @David Dreezer.
Actually, there IS a slight difference between time on Android and time on desktop (Windows 10), but both of them are in their default config, so the thing is expected to work in THIS setup.
I not only reinstalled Google Authenticator but also manually asked for time sync in the options.
Also, I forgot to mention that before now I got the error in the past on Chrome on Android, on the same phone as the ga. However, I never use Narrative on the smartphone so I didn't pay much attention, but I remember to have tried more than once, without success. So, I just tried NOW, and... I get the same error of invalid code on Android, trying to set the 2fa.
It seems impossible to setup the 2fa, now, both from desktop and Android.