Self-hosted applications

Bookmark managers

Shaarli : PHP
Personal, minimalist, super-fast, database free, bookmarking service

Calendars & Contacts

Servers

DAViCal : PHP
Server for calendar sharing
Radicale : Python
Simple calendar and contact server
sabre/dav : PHP
Most popular WebDAV framework for PHP. Use it to create WebDAV, CalDAV and CardDAV servers
Xandikos : Python
Lightweight yet complete CardDAV/CalDAV server that backs onto a Git repository

Development platforms

GitLab Community Edition : Node.js/Ruby
Open source end-to-end software development platform with built-in version control, issue tracking, code review, CI/CD, and more
Gogs / Gitea : Go
Painless self-hosted Git service / Community fork
sourcehut : Python
Open source software suite for managing your software development projects

Email

Clients

Mailpile : Python
Free & open modern, fast email client with user-friendly encryption and privacy features
Roundcube : PHP
Browser-based multilingual IMAP client with an application-like user interface

Servers

Dovecot : C : retrieve
Open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind
OpenSMTPD : C : send
FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with some additional standard extension

Feed readers

Feedbin : Ruby
RSS reader with a beautiful reading experience
FreshRSS : PHP
Free, self-hostable aggregator
Miniflux : Go
Minimalist and opinionated feed reader
selfoss : PHP
Multipurpose RSS reader, live stream, mashup, aggregation web application
Tiny Tiny RSS : PHP
Open source web-based news feed (RSS/Atom) reader and aggregator

Reference: https://www.devolve.net/self-hosted-open-source-rss-readers/

Read later

wallabag : PHP
Self hostable application for saving web pages

Wikis

DokuWiki : PHP
Simple to use and highly versatile Open Source wiki software that doesn’t require a database
MediaWiki : PHP
Free software open source wiki package written in PHP, originally for use on Wikipedia

Note

Alternatively, use a static site generator paired with a development platform and continuous deployment. This wiki uses Sphinx, GitLab, and Netlify, respectively, to cover those three bases.