Open this link in Safari, wait for “Ready offline”, then tap Share → Add to Home Screen → Add. If shown, keep Open as Web App enabled. Open the Home Screen app once while online and check “Ready offline” there too.

Share the link through WhatsApp or Telegram. Each person gets their own empty tracker. Entries stay on this device and are not synced. Export backups in Settings: clearing site data or removing the app can erase local records.