https://twitter.com/waterfoxproject/

Waterfox Web Browser @Waterfoxproject
DRM issues seem to be affecting Prime Video only. If you are
getting issues with other websites, this is likely due to user agent.

Waterfox Web Browser @Waterfoxproject
You can override for each website using an about:config string pref
such as "general.useragent.override.<website>.com" and value
"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0"
https://twitter.com/5chan_nel (5ch newer account)