Learn Chess Basics freezes in Safari iOS browser?

When I use my iPad running iOS 14.4 and Safari browser to access the lichess.org website, I experience the following problem.

1. Select Learn and then Chess Basics,
2. Select the first piece, Rook, and a white box "Stage 1: The Rook" appears in the middle of the browser window.
3. Click on "Let's Go!" button, and a sound plays but the browser window freezes. The white box "Stage 1: The Rook" remains on the screen, but I cannot get to the chessboard behind the white panel to start the exercise.
   Refreshing the browser window does nothing. Hitting the "back" button on the browser does nothing. The only thing that works is to close the browser window and start over.
   When I try the same thing (Learn/Chess Basics/Rook) on a Safari browser on my Mac, it works OK.
   I checked that pop-up blockers are off on the iOS Safari browser settings.
   Any suggestions?

Can you try via Private browsing on iOS?

If that works in a Private browsing window, go to Settings > Safari > Advanced > Website Data, then tap Remove All Website Data.

@tfeledy funny, I just posted about this as well yesterday.

@Schtaeve no, that did not fix the problem. in my post I go into more detail about the fact that it works in older iOS devices (14.x vs 12.x)

https://lichess.org/forum/lichess-feedback/learn--chess-basics-lessons-broken-on-newer-ios-devices

@arfs hmm maybe something Javascript related? I'm not sure if lichess uses Javascript but my suspicion is something on the newer iOS is blocked as they're a lot more aggressive with anti-tracking etc. (albeit Lichess doesn't have any trackers/ads, it might be something like that)

Can you check this:

Open the Settings app on the iPhone or iPad.
Scroll down and choose the Safari browser from Settings.
From Safari Settings, scroll down to the bottom and tap on the Advanced menu.
If it's not already, toggle the JavaScript button to turn ON and enable execution.

@arfs right using your repro I'm getting the same on my device. So yeah gotta be a bug somewhere.

@tfeledy it didn't even occur to me to try the same steps as you to check if it's localised. Dunce cap for me!

@toadofsky are you aware of this issue please? See post #1 for steps to duplicate

iPhone X, iOS 14.4

Same thing with me, but a couple of days ago I found out that if you had a DIRECT LINK to the second one in the course, you can do it like that.

Hello,

It's a known issue: https://github.com/ornicar/lila/issues/7591 but unable to track the source of it, and Safari is only reasonably supported by lichess so not high priority.

After posting this topic, I tried it on an older iPad running iOS 12.5.1 and it worked OK, as arfs says above.
I wish there was a way to text search these posts so I could have found his and others sooner.

@Solal35 the bug is not specific to Safari, but to Webkit.

since all browsers are forced to use the WebKit engine on iOS devices it means that Chrome, Firefox, Brave, or any other browser also do not work. Essentially, the Chess Basics section do not work at all on any new iOS device with 14.x.

Since it's open-source and I'm also a software developer, I may take a stab at troubleshooting it.

@arfs that would be greatly appreciated