I just got a new MacBook Pro and installed QGIS 3.8 yesterday. I had several GDBs working on Ubuntu and QGIS 3.4 but that same GDB will not import in 3.8 on the MacBook Pro. They are vector layer databases and not raster files.
I've been converting the GDB to GeoPackages (on the Unbuntu/QGIS 3.4) which are much faster and flexible. But I can't get much to work on the MacBook in the way of the GDB files.
I used the new package installer from the QGIS download page and noticed it streamlined the installation from previous MacOS installs but I'm wondering if maybe the 3.8 package was ready for distribution yet.