If you attach a smart card reader while tlclient is running, this reader won't be usable: tlclient will not find any smart cards in this reader. It is necessary to restart tlclient to use the new reader.
This makes it much more cumbersome to use Yubikeys with ThinLinc, as they can emulate smart card readers with a built-in card.
See also: bug 7253.
Fixed now. Only tested on Linux so far.
It doesn't work on Windows if you remove the last reader and re-insert it.
It turns out that modern Windows stops the smart card service when the last reader is removed. Any application then needs to re-establish the context once a reader is backed.
Upstream OpenSC has already fixed this, but it wasn't in the last stable release. So let's apply their fix.
Tester should make sure to test both with multiple readers and just one.
Works well now, tested build 6057 on both Windows 10 and macOS 10.14.
Tested plugging in smart card readers with a card already inserted, tested with both one reader and two at a time.