Can not find them util now
Never used duplicity before so let find out together,
Going to try to restore test.odt
my backup disk(participation) is /dev/sdb1
mount /dev/sdb1 /mnt
ls /mnt
output here:
total 20
drwxr-xr-x 2 root root 4096 Feb 24 18:07 labns01
drwx------ 2 root root 16384 Feb 24 18:01 lost+found
show status with backup dates:
duplicity collection-status file:///mnt/labns01/
lets look for my test file test.odt
duplicity list-current-files file:///mnt/labns01/ | grep test.odt
output here:
Tue Feb 23 11:36:27 2021 var/lib/nethserver/nextcloud/admin/files/test.odt
duplicity --file-to-restore var/lib/nethserver/nextcloud/admin/files/test.odt file:///mnt/labns01/ ./test20210324.odt
with -t 1M option you go back one month : (do not have an ald backup so can not test)
duplicity -t 1M list-current-files file:///mnt/labns01/ | grep test.odt
duplicity -t 1M --file-to-restore var/lib/nethserver/nextcloud/admin/files/test.odt file:///mnt/labns01/ ./test20210324.odt
If this does not work we could try to go back to 7.5 (still doubt this would help 
)
EDIT: exact date
duplicity --time 2021-02-24 --file-to-restore var/lib/nethserver/nextcloud/admin/files/test.odt file:///mnt/labns01/ ./test20210324.odt