First of all, I appriciate Calamity and Ves for their nice works on 15kHz output and GroovyArcade.
I used GroovyArcade system released on 2020.4 ver. and it works great.
My CRT has geometric & notification text blinking issues, but now these issues are solved for mame/ume games and advmenup by configuration of CRT_range0 values in mame.ini and modeline tunning of xorg.conf.
I satisfied with Sega Genesis & NES games with UME, but do not with SNES especially Final Fantasy V because of its bad running in openning thema.
I tried with additional emulators like mednafen, but I cannot find option to manage geometry.
When I used GAs released 2018 & 2019.2 (nonstable version maybe), I wrote "monitor=custom" in switchres.conf then the custom value of CRT_range0 in mame.ini seems work.
But when I tested with GA released 2020.4, setting of "monitor=custom" in switchres.conf is not required so I think groovymame now indivisually work in this version of GA.
Search demon have not work in this site, so I use google for manage geometry for mednafen in GA but I failed.
Any link or document will be helpful for me.
Thank you for your attention.