Why would someone do this instead of using the Tor browser for both Tor and i2p sites?
If your running linux do this:
1. install tor and i2pd "sudo apt install tor" and "sudo apt install i2pd"
2. Find the proxy settings in FireFox (settings -> general -> network) or at your system level (settings -> network -> network proxy -> automatic)
3. Paste this URL as the configuration URL https://cdn.hzrd149.com/20ae592ff0761399537dbc20089003e3ed52f16494ebfe1ae759f5527d2c53ba.pac
4. Access any .onion or .i2p site (or nostr relay) using FireFox or any other browser on your system
FireFox network settings:
GNOME network settings
Discussion
You can use the tor browser, its much more secure. but with this you visit .onion sites in your default browser so you don't need to switch browsers just to open tor sites
But it's less secure, so why di that? It's such a slight inconvenience to open another browser. They're already using Tor/i2p, so willing to accept inconvenience for privacy.