Sometimes, but that’s it. Authorities and signal itself can only say “this number has account with us since $signupDate and used it last on $usageDate”. Signal can’t say “we know $number is talking to $otherNumber” nor can they say “$number is in $group talking to $users”.
Same in a few other European countries. I’m doing it right now with a few SIMs. You can also go on holiday to another country, get a few temporary SIMs there for a few quid and fly back home with the “contraband”. Really not hard.
Signal doesn’t collect IPs and therefore can’t even hand them out. It’s been requested in 2021. Here’s a list of requests from authorities they were allowed to publish. I’ve looked through 3 of the most recent and nowhere do they reveal IPs.
I saw some threads here about Telegram and piracy stuff being banned. So, as an experimental alternative, I created a public Signal group for piracy.
Maybe it'll be useful?
Before joining
==========
Signal supports usernames and hiding telephone numbers. Here's a [blog entry on how to do so](https://signal.org/blog/phone-number-privacy-usernames/). You might want to:
* set a username
* change your profile name (these are two separate things!)
* hide your phone number
Then create a simplex group and invite everybody there.