I have a home Asterisk setup, and it's nearly 20 years old. It has a ton of vestigial configurations, including SIP and dialplan integrations with two former employers (one of which has been defunct for nearly 15 years).
These days it only has a single SIP provider (voip.ms), and serves two ATA adapters injecting the home POTS and payphone, both of which I was working on this weekend. I also have some SIP phones in storage, including a few SPA504Gs.