Txt2img with upscaler (with scale ratio version) workflow in comfyUI.
Click "workflow" to check the Image upscaler workflow.
Or Click "Try" to generate image.
At this template U can chage scale ratio at below.
Base img size : 512*768
1st upscaler size : Base img size *4 = 2048*3072
2nd upscaler size : 1st upscaler size *scale ratio 0.5 = 1024*1536
(Maybe the scale ratio 0.5 is a maxium for free user.)