It could allow transparent use of Firefox and Chromium data with the same account with history, passwords, bookmarks shared and the rest of the options and add-ons segregated by browser.
Firefox sync also has "Send Tabs", which -to me- is a great feature.
Yes. I'd love to see a Firefox Sync implementation for Chromium, which would make it easier for people who use Firefox but occasionally need to run Chromium to open something that doesn't bother to handle browser compatibility.
Brave Sync would probably be a better fit. Brave is already built on top of Chromium, it's open source, and they recently "rebuilt [it] to be more directly compatible with the Chromium sync system" [1]. It's also E2EE and doesn't require an account.
I think what you're describing are the "Tip" buttons which can be added on a few supported sites (which can be disabled). They aren't selling anything- it's a feature which people can use if they like.
The server implementation for sync is mostly compatible with Chromium and can be used without Brave. Someone could clone https://github.com/brave/go-sync and stand up their own server. It would require some patches on top of Chromium (similar to what is done in Brave) to implement the authentication - but once that is done, all of the Chromium tools like chrome://sync-internals work just fine
The service itself is open source and can be hosted by a community. It has a different authentication scheme (ex: not Google accounts) and enforces client side encryption by default. See https://github.com/brave/go-sync for more information
The official service hosted by Brave is only intended to be used with Brave Browser
It could allow transparent use of Firefox and Chromium data with the same account with history, passwords, bookmarks shared and the rest of the options and add-ons segregated by browser.
Firefox sync also has "Send Tabs", which -to me- is a great feature.