This seems to have been a big for as long as Steam's existed; see #1050 and #6. Further discussion can also be found on swaywm/sway#1865.

Essentially, Steam expects to be able to grab focus whenever, whereas this is not always the case. The end result in Sway's case is that hovering over tooltips works, but you can't actually click them; instead, you have to press enter to click.

You can test this by running Sway 1.0 on any distribution; in particular, I'm using a recently updated version of Arch Linux with the latest Steam, although this bug has existed for a while.

I don't know how exactly steam is handling the focus for tooltips, but it seems to be both more complicated than it should be, and incorrect. While clients like Sway are not supported, the shift to Wayland will slowly mean that more and more people will experience this bug, and this bug should be fixed before a large number of clients start using stricter focus settings.

Clearer steps for reproduction:

1. Open Sway 1.0 (or later), then open steam.
2. Right click a game in the library.
3. Hover over "properties" in the tooltip. Notice that it lights up when you hover over it.
4. Try to click "properties." Notice that this does not work, and that clicking doesn't affect the tooltip or the window below it.
5. Right-click the game and hover over "properties," this time pressing enter instead. The properties GUI should open.

If anyone has a similar reproduction in a different window manager, please post here as well!