Man pages matching name log4tango::ostreamappender in section 3:

log4tango::OstreamAppender.3.en	debian 10 / liblog4tango-doc
log4tango::OstreamAppender.3.en	debian 11 / liblog4tango-doc
log4tango::OstreamAppender.3.en	debian 12 / liblog4tango-doc