I didn’t have a bell wire either. It wasn’t very hard to add the AC adapter that @SmOothie mentioned. It did require me to crawl in the crawl space under my home to do the wiring or you can just do a wall mount wire to outside to power the doorbell.
Hey I used the Ethernet wires from my previous crappy doorbell.
I have a ring plug in adaptor 24v 2vac that’s wired into the Ethernet wires (cores doubled up for each pairing) and it’s got a plug symbol constantly next to the doorbell on my app.
The spur from the alarm panel couldn’t have worked as it was already transformed to DC power.