03046512336612478855 Sounds like the scrapeable data is plausibly just:
Signal - phone # used on signup
If you have my phone number, and I have not marked it as hidden from search in my Signal account settings, then the phone number can be looked up by anyone from within the Signal app – The presence of a Signal account associated with a phone number can be established that way. But Signal doesn't otherwise publicly publish a list of phone numbers.