Drupal 11 uses jQuery 4. But jQuery.type() is deprecated and no longer available in jQuery 4. Therefore the library does not work out of the box in Drupal 11 installations.
Uncaught TypeError: $.type is not a function
at HTMLInputElement.<anonymous> (jquery.datetimepicker.full.js?t2bnbx:2631:10)
at T.each (jquery.min.js?v=4.0.0-beta.2:2:2876)
at T.each (jquery.min.js?v=4.0.0-beta.2:2:1386)
at $.fn.datetimepicker (jquery.datetimepicker.full.js?t2bnbx:2591:8)
at HTMLInputElement.<anonymous> (drupal.single_datetime.js?t2bnbx:134:35)
at T.each (jquery.min.js?v=4.0.0-beta.2:2:2876)
at T.each (jquery.min.js?v=4.0.0-beta.2:2:1386)
at Object.attach (drupal.single_datetime.js?t2bnbx:63:70)
at drupal.js?v=11.2.3:166:24
at Array.forEach (<anonymous>)
D11 with single_datetime fully set up, try to select a date, not possible at all, get above error.
Active
2.0
Code
Ah looks like it got fixed already upstream here https://github.com/xdan/datetimepicker/pull/761/files
So we probably just need to bump the lib
Damn: The fix is from 2020, but last tag is from 2018