Ubuntu
Ubuntu is a complete desktop Linux operating system, freely available with both community and professional support. The Ubuntu community is built on the ideas enshrined in the Ubuntu Manifesto: that software should be available free of charge, that software tools should be usable by people in their local language and despite any disabilities, and that people should have the freedom to customise and alter their software in whatever way they see fit.
CentOS
CentOS as a group is a community of open source contributors and users which started in 2003 and has been sponsored by Red Hat since 2014. CentOS Linux versions up to CentOS Linux 8 are 100% compatible rebuilds of Red Hat Enterprise Linux, in full compliance with Red Hat's redistribution requirements.