Android app rotates even when device rotation locked

As mentioned in title, the UrzaGatherer Android app rotates between landscape/portrait when tilted, even if the device has "Auto-rotate screen" disabled.

I suspect this is just a general change that was made to web apps in some recent version of the Chrome/Chromium engine, but have not been able to find a way to disable it through browser settings.

Anyway, it's pretty annoying in my case, since I often like to browse through my decks/cards when lying on my side, and this auto-rotate makes it unusable.

That said, thanks to the power of browser extensions, I have found a workaround: (until a better solution is found, or the original Chromium-engine bug/change is fixed)

1) For UrzaGatherer, use an Android browser that supports extensions -- by setting that as your default browser, or using it to add a homescreen shortcut to urzagatherer.app. (I use "Kiwi Browser" personally, but Firefox should also work -- once the deck-clickability issue here is fixed anyway)

2) Install the TamperMonkey or ViolentMonkey user-scripts extension.

3) Type/paste a user-script with the following content, and enable it:

// ==UserScript==
// @name UrzaGatherer rotation-locker
// @match https://*.urzagatherer.app/*
// ==/UserScript==
document.body.addEventListener("click", async ()=>{
    await document.documentElement.requestFullscreen();
    await screen.orientation.lock("portrait-primary");
});

Now if you close then reopen the UrzaGatherer app/page, it