After a fix added to chef_site-type.vm in
SAK-22994 which was deleted by a branch merged in SAK-22450, no extra site types were displayed in Sakai but course, project and portfolio site types (with multiple values configurable in sakai.properties)
Another commit in
SAK-23775 fixed the portfolio site types but prevented any other custom type site and disabled the properties projectSiteType, courseSiteType and portfolioSiteType because of a bad logic.
Currently only projects, courses and portfolios are available to users, no matter the configuration of sakai.properties.
I have a little patch that solves this issue. I plan to submit a PR tomorrow.