Apex domains cannot have CNAME records.
Question and response
Question
dig dedibox.fr. NS
Answer
dedibox.fr. 5 NS nsa.online.net.
dedibox.fr. 5 NS nsc.scaleway.com.
dedibox.fr. 5 NS nsb.online.net.
dedibox.fr. 5 NS nsb.scaleway.com.
dedibox.fr. 5 NS nsa.scaleway.com.
dedibox.fr. 5 NS nsd.scaleway.com.
Authority
The response has no authority records.
Additional
nsa.online.net. 4 A 62.210.16.10
nsa.scaleway.com. 4 A 51.159.69.138
nsb.online.net. 4 A 51.159.78.59
nsb.scaleway.com. 4 A 51.159.47.9
nsc.scaleway.com. 4 A 51.158.139.22
nsd.scaleway.com. 4 A 151.115.8.9
nsa.online.net. 4 AAAA 2001:bc8:1:0:0:0:0:8
nsa.scaleway.com. 4 AAAA 2001:bc8:808:1:0:0:0:9
nsb.online.net. 4 AAAA 2001:bc8:1203:242:0:0:0:1
nsb.scaleway.com. 4 AAAA 2001:bc8:808:1:0:0:0:7
nsc.scaleway.com. 4 AAAA 2001:bc8:5008:200:0:0:0:9
nsd.scaleway.com. 4 AAAA 2001:bc8:1c08:100:0:0:0:6
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0