🎉 Improvements

Allow filtering abstracts by custom fields having no value (#5033, #5034)
Add support for syncing email addresses when logging in using external accounts (#5035)
Use more space-efficient QR code version in registration tickets (#5052)
Improve user experience when accessing an event restricted to registered participants while not logged in (#5053)
When searching external users, prefer results with a name in case of multiple matches with the same email address (#5066)
Show program codes in additional places (#5075)
Display localized country names (#5070, #5076)

🐛 Bugfixes

Show correct placeholders in date picker fields (#5022)
Correctly preselect the default currency when creating a registration form
Do not notify registrants when a payment transaction is created in "pending" state
Keep the order of multi-choice options in registration summary (#5020, #5032)
Correctly handle relative URLs in PDF generation (#5042, #5044)
Render markdown in track descriptions in PDF generation (#5043, #5044)
Fix error when importing chairpersons from an existing event (#5047)
Fix broken timetable entry permalinks when query string args are present (#5049)
Do not show "Payments" event management menu entry for registration managers (#5072)
Replace some hardcoded date formats with locale-aware ones (#5059, #5071)
Clone the scientific program description together with tracks (#5077)
Fix database error when importing registrations to an event that already contains a deleted registration form with registrations (#5078)

Add event.before_check_registration_email signal (#5021, thanks @OmeGak)
Do not strip image maps in places where HTML is allowed (#5026, thanks @bpedersen2)
Add event.registration.after_registration_form_clone signal (#5037, thanks @vasantvohra)
Add registration-invite-options template hook (#5045, thanks @vasantvohra)
Fix Typeahead widget not working with extra validators (#5048, #5050, thanks @jbtwist)