Upgrade Chef-Server 12.16 to 14

Hi, I'm searching on internet but i don't find a valid how to for an upgrade and a compatibility matrix (I read a message here where it seems it doesn't exist at all)

Actual: chef-server 12.16 on CentOS 6.5, + various chef-client 12.16 on various node running CentOS 6.5 to 7.8.

I need to deploy new nodes on CentOS 8

First question:
I see that chef-client 13 (and I suppose 12) is not compatibile with CentOS8 (I read on a github a post here: https://github.com/chef/chef/issues/10225 )

But

Chef-client 14,15,16 aren't compatibile with Chef-server 12 due various deprecations.

This means that I need to upgrade chef-server to 13 or better on 14, on a new server, then, migrate my cookbook and repo structure.
But before i need to upgrade to chef-server 12.17.15 rIght? >> https://docs.chef.io/upgrade_server/#standalone-upgrade
What means this new licence?

Are there some specifications that I need to follow?

What makes you think 14, 15 and 16 are uncomptible with chef server 12 ? That's not the case at all.

Latest "free" chef-server package is 12.19.31 and latest free client package is 14.15, they work together.

If you want to give a try to higher versions, you should contact a sales rep from chef for a license or have a look at https://www.cinc.sh for the community distribution client. (server under work)

On bootstrap on the client (CentOS 8) , shows licence error or
windows/libraries/windows_package.rb:11:in `<top (required)>

googling around could be cookbook version (I can't upgrade right now) or here
https://docs.chef.io/release_notes_client/
windows_package has many changes.

Here a Chef Staff member

"Each product is supposed to work with +/- 1 major version of the other"

So bootstrap of 15 and 16 will indeed barf about the license.

The windows_package error sounds more linked to the windows cookbook as a lot of its resources have been included in core in 15.

The answer from Kallistec is 5 years old, the way Chef Client is versionned has changed since then and this affirmation doesn't stand anymore (chef-server 13 and 14 are pretty recent, chef-server 13 has come after chef-client 15 for the licensing change).

If you don't have licenses, your best bet as upgrade is latest 14 and latests chef-server 12, but this will require fixing the changes in your cookbooks.

I can't tell exactly when support for Centos8 came from memory.

Thank you, so the points are:

  1. No information about Chef-server 12.16.14 with client 14,15,16 for centOS8 is official supported, and/or
    a lots of deprecation from chef 12.16 to 12.19 or 14 need changes in the cookbooks.
    No information about chef-client 12 with chef-server 13-14 will be supported. In case I need to upgrade all clients in actual nodes.

  2. Chef licence for 12.19 is free, 13,14 no

  3. Packages like Nokogiri & Co. are supposed will works with chef-server 12.19 with minor upgrade, with 13,14 need to be upgraded (do need check compatibility with the deploy packets and management)

  4. need to check Chef-Workstation

Situation
CHEF SERVER
CentOS 6.5
Chef-Server 12.16.14

CHEF NODES
CentOS 6.5 to 7.8
Chef-Client 12.16