Nothing else syncs to my phone in a manner that "just works" and doesn't require excessive fiddling, or using k9mail which appears to quite simply not work at all.
So with that said, how does a person use git via email with the Gmail ui?
* for sending patches, use git-send-email from the command line
* for reading, use a greasemonkey script to make gmail use a fixed width font
* when I need to apply a patchset locally I use the "patches" tool https://github.com/stefanha/patches
I also have a couple of gmail "canned responses" set up for things like "write my reviewed-by tag into my email reply".
It's not fantastically ergonomic, but it's good enough that I haven't really felt the need to use something other than gmail web interface.
Before I switched to iOS devices, I used k9mail as I was looking for an email client that did "push" IMAP as I've self-hosted forever and a day. From that experience I'd say that k9mail is more a symptom of the Android ecosystem than an indication that Gmail is just that good. k9 worked for me, but was finnicky if I remember.
On iOS IMAP is very much a second-class citizen. But... with the stock mail client IMAP has been more reliable than Exchange.
> So with that said, how does a person use git via email with the Gmail ui?
Unsure, but if you can you can definitely use Gmail with other clients (for the time being).
k9mail is a dumpster fire in my experience.
Generate an app-specific token in Gmail and use it to configure git for sending mail. For receiving and commenting on patches, you might be able beat the Gmail interface into submission but it's not going to be convenient, if only for the browser restrictions on calling external commands (like git). Maybe with a browser extension.
In any case, you can use a real mail client in parallel to Gmail (the UI) and use whatever is the most suitable tool for the task at hand.