https://web.skype.com/
https://www.ghacks.net/2019/03/08/the-n ... -or-opera/
The quote above is incorrect.....A simple user-agent change is not enough to make Skype for the Web work in unsupported browsers. Microsoft offers no explanation as to why the new web-based version of Skype does not work in Firefox or Opera.....
I found that with the spoofing of the single website:
general.useragent.override.web.skype.com:
" Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3163.100 Safari/537.36"
Chrome 73 on Windows 10.
It works.