WikiSuite can be seen as a FLOSS self-hosted alternative to the various IBM apps (which are typically proprietary).

Apps

Sametime -> Jitsi Meet
Notes -> WikiSuite vs Lotus Notes
DB2 -> For end user databases: Tiki Trackers. For a more traditional relational database, use the same as Tiki: MySQL or MariaDB
Lotus Quickr -> Tiki Wiki, File Gallery, etc.
Connections -> Tiki Blog, Tiki Forums, Tiki Workspaces, Tiki Social Networking, etc.
Lotus SmartSuite -> "In May 2013, IBM announced the withdrawal of SmartSuite. Marketing of the product ended in June 2013, followed by all support ceasing in September 2014. IBM has also announced that there will be no replacement for SmartSuite"
- Lotus Word Pro -> Tiki Wiki with or without WYSIWYG
- Lotus_1-2-3 -> Tiki Spreadsheet
- Lotus_Freelance_Graphics -> Tiki Slideshow
- Lotus_Approach -> Tiki Trackers
Lotus_Symphony -> "IBM discontinued development of Lotus Symphony in January 2012 with the final release of version 3.0.1, moving future development effort to Apache OpenOffice, and donating the source code to the Apache Software Foundation."

Other alternatives