I change the password of my Google account on a frequent basis. My password is always a quite long alphanumeric string generated by a password manager. Typing it is really annoying, specially on a touch interface, so usually I copy and paste it. It works in-browser, but I can't use long pressing to copy and paste on the "Google Signin" screen.
Let me be more clear. When I change it from the desktop web interface, a few moments later my phone complains about an "Account action required".
Clicking the notification shows me a (native, browserless) screen that says:
Couldn't sign in: you typed an incorrect password or your account has changed. Re-type your password. If you forgot your password and need to recover your account click here.
Then it shows me another non-browser screen where it expects me to type my password. On this screen, I can paste as usual, by long-pressing near the cursor and then waiting for a "paste" button to apper.
So far, so good. However, I have two-factor authentication turned on, and just typing my password isn't enough. I see a second screen that says:
Couldn't sign in: To access your account, you must sign in on the web. Touch Next to start Browser signin.
Then it opens what seems to be a browser-within-a-window, with my email address already typed and waiting for my password. The problem is, I can't paste on this screen. Long pressing does not show the "paste" button.
And if I trick it into showing me the button, then I can't submitting the password: I have followed this answer on a related question (writing a single characther and then long pressing), but then pressing the submit button produces no result at all.