is there any way to host everything and not go via zerotier service ?
Each linux/macOS/Windows install is capable of being a network controller. That is free to use as long as you’re not reselling access / setting up a ‘Software as a Service’ model with it. Documentation on the controller API can be found here: https://github.com/zerotier/ZeroTierOne/tree/master/controller
I have been working on this for the past few weeks. Assuming that you just want to have your own network controller, then the answer given by @zt-grant works fine. There are also a few third party open source GUIs if you want to use those as well. Just remember to check the specific licenses they are protected by and what they entail.
However, if you want to have it completely disconnected from ZeroTier you need to create your own root servers and modify the ZeroTier config files. The following link has an instruction on how to do this. https://gotz.co/2019/02/17/mpls-over-zerotier-pt-1/