@rfc2822 I used the automatic Gmail setup from FairEmail to get access to that email inbox. Due to the fact that I’d set-up my phone the ususal way, by linking it to my Gmail account, all default apps, like e.g. the default email program, worked out-of-the-box on my Samsung phone. FairEmail was able to take over these Gmail credentials without any problems.
Unfortunately I cannot tell you if it also works without a preconfigured Gmail account.
That’s what I have assumed from the source code. But I also assume that it will only work with a preconfigured Google account, and users who use DAVx⁵ with Google often won’t have a Google account set up (otherwise they wouldn’t need DAVx⁵ and could just use the normal Google sync).