It looks like the developers weren’t able to update Calomel in time to be compatible with the Firefox 57 release. Would you be interested in reaching out to them and asking about their update status?
On Calomel’s listing page, the developers suggested using Firefox’s Network Security tab to retrieve the same TLS information the add-on was collecting:
To use Firefox’s Network Security tab:
- “Ctrl-Shift-Q” to open the Network window
- Load or re-load the web page
- Click on the top HTML document
- Choose the “Security” tab in the right hand window