ProtonDB which lists Steam Deck as a separate category. Usually you will find users describing their settings if modification is needed.
ShareDeck specifically for Steam Deck settings.
SteamDeckHQ which has Steam Deck settings as well.
Show Great on Deck as a Browser extension (Firefox/Chrome) which displays ProtonDB and SteamDeckHQ on the Steam Store and links directly to the correct subpages.
It uses user submitted titles and thumbnails if they are available. If not, it uses a random frame from the video as a thumbnail and applies some rules to the title (like no caps etc.).
For example a LTT video from yesterday:
Original title: ‘Only YOU can fix GPU pricing… Here’s how!’
Replaced title: ‘How to find a good deal on a used GPU’
And about the thumbnails, just take a look on YouTube. In general I mean 😄
Pretty sure the Steam Deck plays a sound for notifications and achievments, I do not remember for desktop either though 🤷♂️