I don't think you can use Skype messaging in TB chat, and the only option I'm aware of for managing Skype calls is with TBDialOut, which appears to still work with TB 52.

Thanks! But it's possible to chat on a Thunderbirdᵀᴹ address?

Er, what do you mean by a "Thunderbird address"?

A chat service like Google Hangouts or Skype

Perhaps you mean Telephone numbers of people in your address books?

• https://addons.mozilla.org/en-US/thunderbird/addon/telify/

But it may not work on more current releases.

I only want to know if Thunderbird offers an internal chat without using Hangouts or other services.

In that case, no. It is just a client. It relies on 3rd party servers and networks.