You can now downlaod QGIS 3.4 Long term release repository (most stable version of QGIS 3.x 2019) LTR.
For windows :
Windows 32bit (x83) : Download QGIS 3.4 most stable version of QGIS 3.x 2019 32bit
Windows 64bit (x64) : Download QGIS 3.4 most stable version of QGIS 3.x 2019 32bit
Mac os x : Download QGIS 3.4 most stable version of QGIS 3.x 2019 mac
Manual & user guide:
QGIS 3.4 Training Manual (Read and download PDF) English
Manual & user guide:
QGIS 3.4 Training Manual (Read and download PDF) English