On iOS Safari, tap the three stacked lines on the URL bar (depending on which Safari view you use), tap Website Settings, then you'll see a Request Desktop Website switch, which should persist for that domain.
There a two dropdown menu options for "request desktop" in my Safari, in that menu. Translations might be imprecise because I use German locale.
But one is in a section called "Website actions", then there's another one in a section named "Website settings".
I didn't even notice it myself until now.
In earlier versions (before Liquid glass redesign I guess, which enlarged all dropdown paddings), the latter was called "always request Desktop site for xyz".
