I released devpi-server 6.0.0 at https://pypi.org/project/devpi-server/
There are several previously deprecated things removed in this release,
some changes in behaviour and several new features. Read the changelog
and as always have backups ready before upgrading.
This release doesn't require an export/import cycle and it should be
possible to downgrade again as long as you don't use new options on any
Without replicas it is a drop-in update, with replicas you have to look
out for the required shared secret between primary and replicas and in
case you have to down-grade for some reason make sure all files are
synced. It is recommended to upgrade either everything at once, or the
replicas first and the primary last.