The short answer is
RewriteRule ^dashboard/index - [E=no-gzip:1] SetEnvIf REDIRECT_no-gzip 1 no-gzip
Some explination of that solution
The – means NOOP, E means set variable, 1 is the value. After redirects, the variables are renamed and prepended with REDIRECT_.
This work for php FPM
If you have a mod dso you can use also this
apache_setenv('no-gzip', '1');