The IPTV supplier should recommend which app works best with their platform.
Tell them you are using Fire Stick, what you want, IPTV, EPG, Sky, Movies.
Some also do PLEX for movies/boxset/tv, this is different app and login.
Some also have NetFlix accounts.
So with a fire stick you get all worlds on it.
Sort out a VPN (some apps avaialble with side loading) cheap enough and reliable.