thanks @Tom-Elliott for your answer.
I’m confused i think i did not explained my problem clearly.
Debian 12 is my fog server 192.168.1.200
It serves ubuntu iso’s files via nfs , kernels initramfs via tftp and preseed via http(s).
Ubuntu are workstations i need to deploy Ubuntu iso files are on nfs si i don’t really understand.
Should i copy the fog ca in the iso’s nfs directory ?
Looks weird because i never needed this.
My browser works flawlessly with the certificate.
The only problem is when the boot option tries to get the preseed file via https.