I think they use the main URL. It's probably the best to use, as the testing link will occasionally have less stable (broken 😂) builds on it. The current build on testing is almost at 💯 though 👍

nostr:nprofile1qqsth7fr42fyvpjl3rzqclvm7cwves8l8l8lqedgevhlfnamvgyg78spz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsq3camnwvaz7tmwdaehgu3wvf5hgcm0d9hx2u3wwdhkx6tpdssexaht are you using the Vercel hosted link? It is the most recent version, with better performance.