You might try the #christian tag, or the Christianostr group:

nostr:naddr1qvzqqqyx7cpzqjxv6frc4t2xlzqulwea7wrlz32wsqxrly4tr52u3zx3kna94fmuqqxkx6rjd9ehg6tpdehhxarjxp2w3g

I also have a small list of active Christians on nostr:

https://listr.lol/npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn/30003/naddr1qqgngv3n8qergd3hxvengv3s8ycrqdspzemhxue69uhhyetvv9ujumn0wd68ytnzv9hxgq3qjlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qxpqqqp6nx9tdq8u