With fingerprinting it's not impossible. Quoting a recent Webkit thread[1] in which Google blocked all sign in from non-Safari WebKit browsers:
> But if Google does this properly and uses more sophisticated browser
fingerprinting techniques, Epiphany is done for. This could be an
existential threat for non-Safari WebKit browsers. Nobody is going to
be interested in using a browser that doesn't support Google websites.
Google's expressly-stated goal is to block embedded browser frameworks
and non-supported browsers from signing into Google accounts. The blog
post says: "This block affects CEF-based apps and other non-supported
browsers." It says: "We do not allow sign-in from browsers based on
frameworks like CEF or Embedded Internet Explorer."
> But if Google does this properly and uses more sophisticated browser fingerprinting techniques, Epiphany is done for. This could be an existential threat for non-Safari WebKit browsers. Nobody is going to be interested in using a browser that doesn't support Google websites. Google's expressly-stated goal is to block embedded browser frameworks and non-supported browsers from signing into Google accounts. The blog post says: "This block affects CEF-based apps and other non-supported browsers." It says: "We do not allow sign-in from browsers based on frameworks like CEF or Embedded Internet Explorer."
[1] https://lists.webkit.org/pipermail/webkit-dev/2020-November/...