The Debian Jessie LTS support is officially coming to an end on June 30, 2020. We should continue to support the stable releases until that time (and perhaps for a short period afterwards) but publicise an official drop of support with our 20.05 release as we can't/shouldn't really officially support 20.05 on Jessie for more than a month after it's release (i.e. after Debian has dropped such support itself)
"Debian LTS support for Debian 9 "Stretch" ended on June 30, 2022" The following should both be updated I reckon: https://wiki.koha-community.org/wiki/System_requirements_and_recommendations https://dashboard.koha-community.org/
From https://wiki.koha-community.org/wiki/System_requirements_and_recommendations it looks like we did drop Debian 8/9 support. Please reopen if I am missing something!
I dropped it from the dashboard today too