Self-hosted applications

Bookmark managers

ShaarliPHP

Personal, minimalist, super-fast, database free, bookmarking service

Calendars & Contacts

DAViCalPHP

Server for calendar sharing

RadicalePython

Simple calendar and contact server

sabre/davPHP

Most popular WebDAV framework for PHP. Use it to create WebDAV, CalDAV and CardDAV servers

XandikosPython

Lightweight yet complete CardDAV/CalDAV server that backs onto a Git repository

Development platforms

GitLab FOSSNode.js/Ruby

Open source end-to-end software development platform with built-in version control, issue tracking, code review, CI/CD, and more

GiteaGo

Git with a cup of tea, painless self-hosted Git service

sourcehutPython

Open source software suite for managing your software development projects

Email

Clients

MailpilePython

Free & open modern, fast email client with user-friendly encryption and privacy features

RoundcubePHP

Browser-based multilingual IMAP client with an application-like user interface

Servers

DovecotCretrieve

Open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind

OpenSMTPDCtransfer

FREE implementation of the server-side SMTP protocol as defined by RFC 5321, with some additional standard extension

Feed readers

FeedbinRuby

RSS reader with a beautiful reading experience

FreshRSSPHP

Free, self-hostable aggregator

MinifluxGo

Minimalist and opinionated feed reader

selfossPHP

Multipurpose RSS reader, live stream, mashup, aggregation web application

Tiny Tiny RSSPHP

Open source web-based news feed (RSS/Atom) reader and aggregator

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

Read later

wallabagPHP

Self hostable application for saving web pages

Wikis

DokuWikiPHP

Simple to use and highly versatile Open Source wiki software that doesn’t require a database

gititHaskell

Wiki using HAppS, pandoc, and Git

GollumRuby

Simple, Git-powered wiki with a sweet API and local frontend

MediaWikiPHP

Free software open source wiki package written in PHP, originally for use on Wikipedia

Wiki.jsNode.js

Modern, lightweight and powerful wiki app built on NodeJS, Git and Markdown

Note

Another option would be to pair a static site generator with a development platform. This wiki uses Sphinx and GitLab, see its .gitlab-ci.yml file.