I see that it can be slower because of having all the dependencies included with the flatpak itself instead of relying solely on whats installed on the system. I read that this means it isolates or sandboxes itself from the rest of the system.
Does this not mean that it can't infect the rest of the system even if it had malware?
I have seen people say that it isnt good for security because sometimes they force you to use a specific version of certain dependencies that often times are outdated but I'm wondering why that would matter if it was truly sandboxed and isolated.
Do they mean that installing flatpak itself is a security risk or that also specific flatpaks can be security risks themselves?
There are vulnerabilities found in Flatpak's sandboxing all the time so it's pretty much broken. The opening speed on HDD systems is really really bad too. That's why I only use Flatpak to install software that's not available in my distro's repos. Though I use Arch (btw) so distro packages being old isn't an issue for me.
Yes. 1TB SSDs can be bought new for 50€, 500GB for even less. For some people this is expensive depending in the region (e.g. I also know someone who uses an HDD). But given the price of other pc parts it isn't something to cheap out on (a 1TB/2TB HDD is also 50€).
Do you have current proof that there is security problems in the current stable version of Flatpak? Nothings perfect but bubblewrap should be pretty solid.
Well the sandboxing does help with trustworthy browsers so the websites can't have excessive permissions. But relying on such a broken system isn't a very good idea imo.
Sandboxing in the browser is different than the sandboxing done by flatpak.
You really want your browser sandbox to be rock solid as any weakness allows for drive by attacks by websites.
Flatpak uses bubblewrap under the hood so it is just as secure. Flatpak also has a security tracker and when security issues are found they are taken very seriously.