Not a full list, but these are my day to day extensions that I use the most:
UBlock Origin - (obviously)
600% Sound Volume - managing volume for tabs
Dark Reader - Dark theme, that works well for *most *sites. Sometimes I need to manually disable it for certain sites that don't play well, but that's pretty rare
Fake Data - fill forms with random generated data - for every site i need to sign up for and don't want to use PII
addy.io - extension for add.io email forwarding service (subscription needed) generate random emails for every website i sign up for that direct to my main email. If I start getting spam, I know which alias it came from and which site I made it for
password manager extension of choice - I prefer Bitwarden, but I get a 1Password subscription free with work so that's what I use to share password records with family
firefox container manager - very handy for work tabs, logging in with family credentials, etc
**I checked it out, and there's no reply functionality (which I use especially for support tickets), the email forwarding doesnt have a separate app, so it's a bit clunkier to organize each alias through the duckduckgo app/extension itself. I'll stick with addy.io for my use, but good to know they have that.