General:

Added option to add extra highlighting to the active tab with an extra line of color (off by default.)
Minor tweaks to the GUI style engine to make disabled widgets more distinct from enabled widgets.

Slack:

Fixed sign-in with username & password no longer working.
Fixed file upload no longer working.
Added per-message explicit timestamp in the right-click menu for messages.
Increased per-workspace custom emoji limit from 100,000 to 1,000,000.
Added a workaround for Apple rdar://12345 links being mangled due to URL parsing treating the 12345 part as an integer IP address.
Added gemini:// as a whitelisted URL scheme.
Added snrx:// as a whitelisted URL scheme.
Note for Slack users: there is a known and unresolved issue where your channel sidebar may become cluttered with junk channels named like #mpdm-foo--bar. I know about this and I'm fixing it. The fix for it didn't make it into this version, 0.4.29, because a complete and flexible solution for it involves changing some code that will require heavy testing, and I didn't want to delay releasing an update any longer. Sorry about that.

Discord:

Added a dedicated mute button for other users in voice chats. Finally.
Added ability to bookmark group DM channels. Finally.
Added support for replying to messages in DM and group DM channels.
Added support for newer permissions flags, like "request to speak" for stage channels.
Added a menu item and a toolbar button to join or start DM and group DM voice calls. The only way to do this previously was to right-click on the DM channel in the sidebar. That was stupid. Now there's a regular menu item and toolbar button.
Added guild creation date in the right-click menu for guilds.
Added channel creation date in the right-click menu for channels.
Added anti-spam warning in the "accept invite" menu/dialog.
Changed the URL used when clicking on the thumbnail of an uploaded video so that web browsers will prefer to play the video in a tab instead of download the video as a file to disk. Finally.
Fixed a bug where angle brackets could be treated as Qt's pseudo-HTML text styling markers in the rich embed text sub-view. This was not an exploitable bug. It was caused by Qt's document layout system automatically trying to apply bold, italic, etc. styling if it thought the plain text had HTML-like tags in it.
Fixed unsent input text being cleared when navigating from one Discord channel to another while quick reply input mode is engaged.

Windows:

Ripcord

Alternative desktop chat client for Slack (and Discord)