How to set screen resolution in DietPi for Sparky SBC?

Please explain how to set screen resolution for an monitor in DietPi for Sparky SBC image? I have monitor with resolution 1600x900. If it impossible maybe I can set 1280 × 720?
On boards like the Pine64 with uEnv.txt support simply add a line to provide additional Kernel arguments.
I have added optargs=disp.screen0_output_mode=720p60 to /DietPi/uEnv.txt but it not help.
Odroid C has for this task boot.ini file.
I don’t know how it can be changed in Sparky SBC?
I need settings “1600x900p60hz” | 1600x900 Progressive 60Hz


I replied to your post on Git: