brent flatpak utilizes bubblewrap and I thought for the other apps (browsers esp.)
Why not use Flatpaks instead of trying to roll your own sandboxes? Brave, Chrome, Chromium, Edge, Firefox, Midori, Opera, Ungoogled Chromium, Waterfox and a half dozen other browsers are available on Flathub, not to mention two thousand or so other applications. Just about every mainstream application is available as a Flatpak these days.
Here's a mind game (thought experiment?) for you: Check to see how many of the default Solus applications (other than utilities) are available as Flatpaks.
I've never done that, but my guess is that you could probably replace all or just about all of the Solus default applications you use with Flatpaks. After all, Fedora Silverblue and Fedora Keonite use Flatpaks exclusively, and nothing mainstream seems to be missing from the mix.
Flatpak use is not as convenient as packaged applications on Solus or Flatpaks on other distros like Kubuntu because the team has yet to integrate Flatpak into the package manager. I understand that is coming down the road, but right now you have to upgrade Flatpaks independently of the weekly updates. Not a big deal. I use Flatpaks and update my Flatpaks (Edge and Zoom) right after the weekly updates are completed.