This isn't the site I normally use, but it's another one:

https://grizzlysms.com/signal

You get a unique phone number, signal sends the activation text, you confirm the account. And they add the number to a blocklist so no one else can use that number and screw your account up. I've done it for Discord, Telegram & Signal. I have Signal running in Waydroid right now, without my phone number attached to it