In the player
Every major service includes its own subtitle tracks. Open the speech-bubble or audio menu in the player and pick a language; most apps remember it.
Stand-up and documentaries
Subtitles help with fast talkers and field recordings, so they are worth switching on for specials and documentaries.
Anime
Choose the Japanese track with subtitles or a dub; JUJUTSU KAISEN and SPY x FAMILY are popular both ways.
Original language
Every title page shows the original language before you start.