@omgubuntu@floss.social Just to expand on why it is not official.
The Chromium sandbox is actually very good and it is fully interprocess. My understanding is that Flatpak's sandboxing is typically to separate an app from other apps and/or from parts of the OS. The difference is that in Chromium if you load Facebook in one tab it cannot get access to the process that runs Youtube in your other tab.
But the Chromium sandbox needs greater integration with the OS and the attempts by flatpak to handle sandboxing clashes. Thus all the Chromium browsers and Electron apps use a trick (Zypak) which fakes part of the chromium sandbox.
In short, Flatpak doesn't allow important parts of the Chromium sandbox to work as intended by the Chromium team, when running under Flatpak. So it appears to me that you end up with a key part replaced with something potentially weaker and certainly less well understood and tested. Zypak looks like is maintained by a small team, primarily a single person (that is not to knock them, it is impressive and they clearly know a lot more than me!). But for comparison those responsible for the Chromium sandbox are a bigger and more established team.
Vivaldi
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