cURL is an Open Source project consisting of voluntary members from all over the world, living and working in a large number of the world's time zones. To make such a setup actually work, communication and openness is key. We keep all communication public and we use open communication channels. Most discussions are held on mailing lists, we use bug trackers where all issues are discussed and handled with full insight for everyone who cares to look.
It is important to realize that we are all jointly taking care of the project, we fix problems and we add features. Sometimes a regular contributor grows bored and fades away, sometimes a new eager contributor steps out from the shadows and starts helping out more. To keep this ship going forward as well as possible, it is important that we maintain open discussions and that is one of the reasons why we frown upon users who take discussions privately or try to email individual team members about development issues, questions, debugging or whatever.
In this day, mailing lists may be considered the old style of communication — no fancy web forums or similar. Using a mailing list is therefore becoming an art that is not practiced everywhere and may be a bit strange and unusual to you. It is just about sending emails to an address that then sends that email out to all the subscribers. Our mailing lists have at most a few thousand subscribers. If you are mailing for the first time, it might be good to read a few old mails first to get to learn the culture and what's considered good practice.
The mailing lists and the bug tracker have changed hosting providers a few times and there are reasons to suspect it might happen again in the future. It is just the kind of thing that happens to a project that lives for a long time.
A few users also hang out on IRC in the #curl channel on libera.chat.