GRASS not working with QGIS 3.6

If I open QGIS with the shortcut "QGIS Desktop 3.6.0 with GRASS 7.6.0" everything works fine. If I open QGIS with the shortcut "QGIS Desktop 3.6.0" I get the same error as you

I had the same problem but I managed to solve it by renaming my grass folder from "grass76" to grass-7.6.0".

Based on this grasswiki-article setting the operating system environment variable GISBASE to the GRASS installation folder might fix the issue (e.g. C:\OSGeo4W\apps\grass\grass76).

QGIS 3.8 processing options still doesn't contain an option for the GRASS folder.

I refer to Windows operating system and QGIS 3.8 / GRASS 7.6.