When I've used it, gapless playback being non-existent due to it basically being a frontend to the web client/MusicKit for web. I listen to a lot of albums in full nowadays, so that can really hurt the experience. It's a shame because everything else about it is great. I am aware that the Cider devs are trying to find ways of handling that without reliance on the web client/API, which might enable gapless but also stuff like lossless if you got AM for that.

Edit: I should mention that Cider has a new client that's paid but still supports Linux (specifically with AppImage, .deb and .rpm packages), and my experience was with Cider Classic.