$ DRI_PRIME=0 glxinfo | grep "OpenGL renderer string"
OpenGL renderer string: Mesa Intel(R) UHD Graphics 620 (KBL GT2)
$ DRI_PRIME=1 glxinfo | grep "OpenGL renderer string"
OpenGL renderer string: NV118
$ cat /etc/environment
#
# This file is parsed by pam_env module
#
# Syntax: simple "KEY=VAL" pairs on separate lines
#
DRI_PRIME=1