>>2754374A lot of people use the ultimate upscaler.
ultimate-upscale-for-automatic1111
In my workflow I like to use the highres fix in the main txt2img tab, but some people don't like it because the separate upscaler is able to create bigger images before running out of memory. I personally don't care if my images are really big.
My favorite upscaler is R-ESRGAN 4x+ Anime6B, but I recommend you do your own experiments to see what you like the best.