It does work on Chrome, but seriously. Google has enough power already. 😉
The sign-in code seems to be very fragile - I don't know why. I use SeaMonkey which is a bit of a niche browser (but is really the parent of Firefox), but on my desktop computer I had to clear out a bunch of the databases in my SeaMonkey profile before sign-in would work. Even now it won't show me the list of people who 'like'd a posting - on the other hand it works on the same version of SeaMonkey on my laptop. Weird.
Same here on Vivaldi (Chrome-based). Disabling uBlock and Privacy Badger does not help.
Maybe the problem is that the Google sign-in website is opened in a new window, where ad- and tracker-blocker are still enabled.
Anyway, I had to resort to a Firefox without any extensions to log in and 'connect accounts' or whatever it does on the first log in. And even after that Vivaldi does not log in on the first try.
I had to allow 3rd party cookies in Chrome but really not happy about that.
I am not able to log into this forum using Samsung Internet. I just re-enabled the stock version of Chrome to test if it works with that, and apparently it did. On Samsung Internet i go on the forum site, click sign in. Then i am redirected to the niantic signin page, there i click on sign in with Google. I choose the Google Account used for Ingress from the google Account selector, but then i am again redirected to the Niantic signin page with sign in with Google button greyed out and not clickable anymore. It would be nice to fix the issue because i don't have any memory space left on my device to update Chrome to the newest version and i feel rather insecure browsing with an old Chrome Browser.