Playing Magic The Gathering: Arena on PC via Steam.

When a spell is cast which would cause Kiora, Sovereign of the Deep to trigger two things can happen:

A) If the spell WOULD NOT reveal a spell of lesser mana value which the player would be able to cast then a browser will pop up and show the revealed cards, displaying them as intended.

B) If the spell WOULD reveal one or more spells which could be cast with the trigger, the ability will bug and the browser will not appear. The applicable number of cards will be revealed by being shown face up on top of your library (though you can typically only see the top card or two due to them remaining stacked in your library.

-a) If the top card can be cast as part of the resolution of Kiora's ability then you may select it and do so, however you are not able to select any card under the top card.

-b) If the top card cannot be cast then you cannot cast any of the cards that you would be able to that are also revealed because they are hidden under it and cannot be selected or viewed.

Note that in some cases a card under the top card can be seen sticking out from the bottom of the library. I am not sure what causes this, but you can see an example in my attached screenshots where I was even able to select the revealed card. Unfortunately it was another land in this instance so I am not sure if a spell would be castable if one were to "poke out" in this way during this bug.

Note that using the inspect function (right click) does nothing with any of the cards on your library during this period.

In the case of circumstance B)b) above where you get a "successful" trigger but the top card of your library is not able to be cast (such as being a land) then the only way to resolve the ability is to select either "Resolve" or "Resolve All" to bypass the ability by electing not to cast any revealed spells.

This bug essentially makes Kiora, Sovereign of the Deep unplayable. Please fix