Open-Xchange documentation is sometimes little bit fragmented, but Installation guides are available, example for Debian 11: https://oxpedia.org/wiki/index.php?

Open-Xchange documentation is sometimes little bit fragmented, but Installation guides are available, example for Debian 11: https://oxpedia.org/wiki/index.php?title=AppSuite:Open-Xchange_Installation_Guide_for_Debian_11.0 https://oxpedia.org/wiki/index.php?title=AppSuite:Open-Xchan... Now, those mailbox.org and others use (probably) commercial version. which comes with additional functionality (like document converters for preview) and providers make their own customizations top of that anyway.