I recently switched to LibreWolf as my default browser, and I also wanted links to open by default inside it, but there isn't an option in LibreWolf like in other browsers.
Luckily, there's another way. At least I found a solution for macOS:
- Click the Apple menu  in the corner of your screen.
- Select System settings.
- Select Desktop & Dock.
- Scroll down a bit. Under Widgets you can select your default browser from a list.
That's it! 🎉
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