Authentic Nokia 3.4 Firehose loaders are officially public. However, they have been extracted from leaked OEM service tools or factory firmware. Characteristics of a valid loader:

Because the Nokia 3.4 has Secure Boot enabled, it will only execute a Firehose loader that has been digitally signed by the OEM (HMD Global). A mismatched or unsigned loader will be rejected by the device's Primary Boot Loader (PBL). Primary Use Cases Firehose Loaders - Temblast

Click Download (green arrow). QFIL will:

Android 11 update released for Nokia 3.4: Details here - Yahoo Finance