Boot order change in UEFI

Hello,

I have an issue with a Dell R640 on UEFI.

I set PXE boot on 1st place in boot order, and once installed a ubuntu linux (or other), the boot order change and the boot on disk go first (with ubuntu).

I see other issue about that topic, but no solution..

- Here the same questions on the french forum, but answered is provided in private

- Here someone fixed it with cctk, but it's not available on linux..

What are my options ??