qBittorrent v4.2.0 was released.
There were no significant user facing changes since the previous RC release. The full v4.2.0 changelog follows.
ATTENTION: This release uses the libtorrent 1.2.x series. It saves fastresumes a bit differently than the 1.1.x series, which are used so far in the previous versions. If you run it and then downgrade to a previous qBittorrent version then your torrents will probably start rechecking.

• FEATURE: Libtorrent 1.2.x series are supported now (glassez)
• FEATURE: Add OpenSSL version to GUI and stackdump (Chocobo1)
• FEATURE: Add zlib version to GUI & stackdump (silverqx)
• FEATURE: Use PBKDF2 for the GUI lock. You will need to set your password again. (Chocobo1)
• FEATURE: Rename "#" column to "Tier" in the tracker list (thalieht)
• FEATURE: Allow setting larger checking memory usage in GUI (airium)
• FEATURE: Converted remaining icons to svg (Bert Verhelst)
• FEATURE: Replace CheckBox with Arrow in the side panel (Prince Gupta)
• FEATURE: Log performance alerts from libtorrent (Chocobo1)
• FEATURE: Use native folder icon in content tree (Chocobo1)
• FEATURE: Move copy actions under a submenu (Chocobo1)
• FEATURE: Add "Socket backlog size" option (Chocobo1)
• FEATURE: Add "File pool size" option (Chocobo1)
• FEATURE: Allow styling with QSS stylesheets (Prince Gupta)
• FEATURE: Add "Tracker entries" dialog (Chocobo1)
• FEATURE: Add availability column (Chocobo1)
• FEATURE: Use a randomized port number for the first run (Chocobo1)
• FEATURE: Enable Super Seeding mode once ratio/time limit is reached (thalieht)
• FEATURE: Improve embedded tracker. Now it conforms to BEPs more closely. (Chocobo1)
• FEATURE: Add option to align file to piece boundary when creating new torrent (Chocobo1)
• FEATURE: Ability to open file or trigger torrect action via keypad Enter (Chocobo1)
• FEATURE: Add "Remove torrent and its files" option to share ratio limiting (thalieht)
• FEATURE: Allow to select multiple entries in "banned IP" dialog (Chocobo1)
• FEATURE: Reallow to pause checking torrents (thalieht)
• FEATURE: Reallow to force recheck torrents that aren't fully started (thalieht)
• FEATURE: Add "Preview file" double-click action (warren)
• BUGFIX: Avoid performance penalty when logger is full (Chocobo1)
• BUGFIX: Remove the max half-open connections option (thalieht)
• BUGFIX: Center align the section labels in advanced settings (thalieht)
• BUGFIX: Add documentation links to some advanced settings (thalieht)
• BUGFIX: Impove DownloadManager code (glassez)
• BUGFIX: Limit DownloadHandler max redirection to 20 (Chocobo1)
• BUGFIX: Log DownloadManager SSL errors (Chocobo1)
• BUGFIX: Force recheck multiple torrents one by one (glassez)
• BUGFIX: Close context menu when content model is reset (glassez)
• BUGFIX: Improve Properties widget (glassez)
• BUGFIX: Prevent flickering preview dialog (silver)
• BUGFIX: Rename "Prefer encryption" to "Allow encryption" (thalieht)
• BUGFIX: Fix search icon placement when using RTL languages (Chocobo1)
• BUGFIX: Avoid combo boxes extending to the right in Options dialog (Chocobo1)
• BUGFIX: Fix speed limit not applying to IPv6 peers (Chocobo1)
• BUGFIX: Log failed file rename errors (Chocobo1)
• BUGFIX: Fix wrong "Time Active" value displayed (Chocobo1)
• BUGFIX: Rename priority to queue in the context of torrents (thalieht)
• BUGFIX: Update remaining size of ignored files to 0 (Thomas Piccirello)
• BUGFIX: Move "Check for program updates" checkbox to the Behavior settings (Chocobo1)
• BUGFIX: Improve error messages for URL seed (Chocobo1)
• BUGFIX: Rename share ratio limiting options (thalieht)
• BUGFIX: Fix country name misspelling (horgan)
• PERFORMANCE: Faster/efficient way of handling updates in the Transfer list (Chocobo1)
• WEBUI: Bump Web API version
• WEBUI: Use PBKDF2 for the WebUI password. You will need to set your password again. (Chocobo1)
• WEBUI: Use Javascript strict mode (Chocobo1)
• WEBUI: Remove autocorrect/autocapitalise from filepaths on WebUI (AceLewis)
• WEBUI: Display warning when Javascript is disabled (Chocobo1)
• WEBUI: Remove mootools lib from login page (Chocobo1)
• WEBUI: Prevent login credential appearing in url
• WEBUI: Load WebUI certificate & key from file path (Chocobo1)
• WEBUI: Add migration code for WebUI https related change (Chocobo1)
• WEBUI: Fix wrong element id being used (Thomas Piccirello)
• WEBUI: Fix direction of Web UI sorted column icon (Thomas Piccirello)
• WEBUI: Match WebUI About page to GUI (Thomas Piccirello)
• WEBUI: Simplify tab logic (Thomas Piccirello)
• WEBUI: Separate URL components before percent-decoding (glassez)
• WEBUI: Capitalize event name (Thomas Piccirello)
• WEBUI: Fix bug where input wouldn't always be focused (Thomas Piccirello)
• WEBUI: Add Web UI support for escape key (Thomas Piccirello)
• WEBUI: Fix broken image link (Tom Piccirello)
• WEBUI: Include application version in css/js url for cache busting (Thomas Piccirello)
• WEBUI: Update WebUI img to use svg images (Chocobo1)
• WEBUI: Fix speed limit icon too large on WebUI (Chocobo1)
• WEBUI: Fix misaligned icons in STATUS list in GUI (Chocobo1)
• WEBUI: Drop legacy WebAPI support (glassez)
• WEBUI: Allow WebUI Content tab to be sorted (Thomas Piccirello)
• WEBUI: Encode torrent name before passing in url
• WEBUI: Move WebUI Peers code to separate file (Thomas Piccirello)
• WEBUI: Prevent WebUI tables from being highlighted (Thomas Piccirello)
• WEBUI: Allow WebUI Trackers table to be manipulated (Thomas Piccirello)
• WEBUI: Fix only the first newline char is replaced (Chocobo1)
• WEBUI: Fix missing semicolon in WebUI (Chocobo1)
• WEBUI: Add autocomplete attribute to WebUI (Chocobo1)
• WEBUI: Always use index.html as default page (CzBiX)
• WEBUI: Set title attribute for all WebUI table cells (Thomas Piccirello)
• WEBUI: Align WebUI login button to the right (Chocobo1)
• WEBUI: Use force refresh on WebUI logout (Chocobo1)
• WEBUI: Use a random number for WebUI cache busting (Chocobo1)
• WEBUI: Register protocol handler in WebUI for magnet links (Cory)
• WEBUI: Add WebAPI session timeout settings (Chocobo1)
• WEBUI: Fix encoding of special characters (Tom Piccirello)
• WEBUI: Avoid word wrap in webui footer (airium)
• WEBUI: Add advanced options in WebUI (Zhaoyu Gan)
• WEBUI: Move WebUI copy actions under a submenu (Thomas Piccirello)
• WEBUI: Add WebUI support for triggering context menus on mobile (Thomas Piccirello)
• WEBUI: Implement tag management for WebUI (Vasiliy Halimonchuk)
• WEBUI: Fix WebUI removing parameters from magnet links (Thomas Piccirello)
• WEBUI: Enable by default the search tab (Thomas Piccirello)
• WEBUI: Add context menu to Web UI search table (Thomas Piccirello)
• WEBUI: Display files hierarchically in Web UI content tab (Thomas Piccirello)
• WEBUI: Add ability to add and ban a peer from the Web UI (Thomas Piccirello)
• WEBUI: Increase WebUI window heights (Thomas Piccirello)
• WEBUI: Sort torrent names case-insensitively in webui (airium)
• WEBUI: Support exclusions in WebUI table filters (Thomas Piccirello)
• WEBUI: Don't save preferences until all options are processed (Tom Piccirello)
• WEBUI: Disable port selection when "Use different port on each startup" is selected (Chocobo1)
• WEBUI: Remove max character limit of location path (Clément Pera)
• RSS: Better widget for choosing file path in automated downloader (thalieht)
• RSS: Allow to cancel/retry the fetching of feeds (glassez)
• RSS: Add create subfolder option to RSS auto-download rules (Xegor)
• RSS: Log "RSS Feed successfully downloaded" event (glassez)
• SEARCH: Add default tooltip "Searching..." on tab creation. (paolo-sz)
• SEARCH: Avoid crashes on torrent search (paolo-sz)
• SEARCH: Add right click menu to SearchJobWidget (Chocobo1)
• SEARCH: Rename label in search widget (Chocobo1)
• SEARCH: Add more copy field actions to search widget (Chocobo1)
• SEARCH: Remove buttons from search widget (Chocobo1)
• SEARCH: Update python installer url
• WINDOWS: Drop support for < Windows 7
• WINDOWS: Allow headless builds on Windows (knackebrot)
• WINDOWS: Add option to control qBittorrent process memory priority (Chocobo1)
• LINUX: Add content_rating, release tags to appdata (Peter Eszlari)
• LINUX: Update .appdata descriptions (Chocobo1)
• LINUX: Use reverse DNS convention for metadata files naming (Chocobo1)
• LINUX: Adjust open file descriptor limit on startup to max (Chocobo1)
• MACOS: Drop support for < macOS 10.10 (Yosemite)
• MACOS: Replace deprecated qt_mac_set_dock_menu() (Chocobo1)
• MACOS: Add some padding to macOS app icon (Nick Korotysh)
• OTHER: Raise minimum C++ version to C++14 (Chocobo1)
• OTHER: Raise minimum Qt version to 5.9.0 (sledgehammer999)
• OTHER: Drop support of libtorrent < 1.1.10 (glassez)
• OTHER: Drop upgrade code from older saving systems (sledgehammer999)
• OTHER: Update INSTALL dependencies (Chocobo1)
• OTHER: Optimize PNG images losslessly with zopflipng (Peter Dave Hello)
• OTHER: Optimize svg files using SVGO (sledgehammer999)
• OTHER: QMake: Compile translations at build time (glassez)
• OTHER: Drop support for "BC Link" format (Chocobo1)
• OTHER: Lots of code refactorings, cleanups, improvements and optimizations (Chocobo1, glassez, thalieht)

thank you