Found the issue.
Upgrading to Octopus did replace /etc/init.d/radosgw which contained
some changes to the distribution detection and setting ulimits.
New radosgw init script:
-snip-
echo "Starting $name..."
if [ $DEBIAN -eq 1 ]; then
start-stop-daemon
> In Ceph Nautilus we used to set in ceph.conf the following which I
> think helped is avoid the situation:
>
> [global]
> max open files = 131072
>
> This config option seems to be no longer recognized by ceph.
>
ceph config set ??? (I would not know, I am still Nautilus)
