Web browsers
Text message replacements (cross-platform, secure)
Direct file transfer (secure, no cloud)
OnionShare, Datash, SendSecure, JustBeamIt, ToffeeShare
File Transfer (local network only, no cloud)
File Transfer (secure, temporary cloud)
Tresorit Send, WeTransfer, UploadFiles, FileMail, file.io
File sync (no cloud)
Password management (no cloud)
KeePassXC (hint: combine with SyncThing)
Full Cloud
(e.g. google/icloud alternative: email, contacts, calendar, files, etc.)
Full Cloud (self hosted)
File Sharing, Chat, Team Collaboration
(e.g. Slack alternative: private, secure, with cloud)
Secure Email
VPN (Virtual Private Network)
ProtonVPN (free & paid), NordVPN (paid & good)
Free Office Suite (Microsoft Office Alternative)
LibreOffice (better MS compatibility), OpenOffice
More free and open source source software