There are many alternatives to Bitrix24 as a self-hosted solution if you are looking for a replacement. The best Self-Hosted alternative is TiddlyWiki, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Bitrix24 and many of them are available as a self-hosted solution so hopefully you can find a suitable replacement. Other interesting Self-Hosted alternatives to Bitrix24 are Redmine, OpenProject, DokuWiki and Odoo.
OpenProject is an open-source project management software with a wide set of features and plugins. It supports project timelines / Gantt charts, issue tracking, wiki, document management, time and cost reporting, code management, Scrum and much more.
Odoo (formerly OpenERP) is a suite of open-source business apps written in Python and distributed under the AGPL license, under the Open Core software business model. It is used by 2 million users worldwide to manage companies of all size.
Almost everyone thinks Odoo is a great alternative to Bitrix24.