It was promised from its first technical preview that it would eventually have a built in mail client.
It isn't "bloat" any more than a screwdriver on a Swiss army knife is bloat. It's one of the key features of the browser going forward. If you believe browsers should not have built in mail clients, well, that's why alternatives exist. It's Vim vs the IDE debate, at some point you just have to accept that some people want the bare bones editor and some people want the full featured experience and there's nothing wrong with either approach.
Opera used to have notes and I doubt they ever had a CVE due to it.
I'm not fully sold on "doesn't belong in browser" - arguably, it the browser is almost like an OS, it is not far fetched to ask for such features. I guess that is also what ChromeOS does.
> bloated interface
It looks almost exactly like Chrome to me. I have them side by side and the difference is barely noticeable.
> word processor
I assume you mean its note feature, which I know exists but has never once been used by me nor has it ever gotten in my way.
> minigames
If there are minigames I had no idea they existed. I'm fairly certain Chrome has some though.
> All things work, but none of them work good.
This isn't clear enough to be worth arguing against, but the only thing I'll point out that doesn't "work good" for me is the tab switching interface is sometimes slow and gets "caught" on the tab switching screen. Everything else is business as usual.
> absolutely no tracking protection by default
I'm not sure if they have ever claimed this, nor do I recall if it is enabled by default, but Vivaldi has a built in ad blocker, and you can still install Chrome extensions for additional protection.
> I've found nothing about how their sync protocol works
A quick search for "Vivaldi sync" turned up this: "You also need to pick an encryption password that is used for encrypting your data. Your encryption password is used locally on your computer for encrypting the data you’re about to send to our servers and to decrypt the received data. Your encryption password is never sent to us or any other third party, which ensures that we cannot decrypt your data." [0] (Also linked from the article you're commenting on.)
Maybe that isn't the technical detail you're looking for but it's not "nothing."
[0] https://help.vivaldi.com/desktop/tools/sync/