This seems to be an issue with LineageOS, or maybe the version of your browser.
I tested this in Chrome (version 89) and Firefox (version 87) in Android (version 10) and looks fine:
Also tested it in Safari:
From what I see in the code, seems like you are correct, the only size is 512 px. There are so many devices, browsers and recommended sizes to each one that I guess it’s hard for discourse to cover them all. 512 px seems to work fine for most tough.