Because all the cool kids are doing it. The origin story for this kind of post lives here.
Anyway, here we go.
Mail Service: Mailbox.org
Mail Client: Thunderbird and Mail (iOS)
Notes: Joplin, Pen and paper
Calendar: Thunderbird and Calendar (iOS)
Contacts: Thunderbird and Contacts (iOS)
RSS: Feedbin
RSS Client: Web & NetNewsWire (iOS) (although I am considering Reeder again on iOS)
Cloud: Nextcloud
Photo: iCloud and Photos (iOS)
Web Browser: Firefox and Safari (iOS)
Chat: Signal, iMessage, WhatsApp (thanks, I hate it)
Bookmarks: Raindrop
Read it Later: Omnivore and Kindle Paperwhite
Word Processing: Google Docs & LibreOffice
Shopping Lists: Joplin or Pen and Paper
Music: Bandcamp (for buying and the app on iOS)
Podcasts: Overcast
Passwords: Bitwarden
Social Media: Very sporadic bursts on Bluesky, Mastodon and Instagram
Weather: Weather (iOS)
Search: Brave
Movie Tracking: Letterboxd
TV Tracking: Serializd
Book Tracking: Goodreads
Maps: Apple Maps (iOS)