I've just installed Orion Alpha for Linux and was checking out the extensions page like so
- Menu > Orion > Popular extensions
On this page, there's links to go to the Chrome and Firefox stores

When clicking these links, my default browser (Firefox) opened the pages.

Even though Firefox is my default browser, all links clicked anywhere in Orion should open in Orion.
NixOS 25.11, Orion 2.49.1 (WebKit development)
Linux - Describe Below