We tried to update to PHP 8.1 today and found that datepickers were no longer working. Attempting to select a date blanks the field out and logs the following to the console after a second:
post.php:1 Uncaught SyntaxError: "[object Object]" is not valid JSON
at parse (<anonymous>)
at Function.<anonymous> (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:92835)
at e.<computed> [as parseJSON] (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:91291)
at Object.success (date.js?ver=0.1.2:8:180)
at c (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:28447)
at Object.fireWith [as resolveWith] (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:29192)
at l (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:80176)
at XMLHttpRequest.<anonymous> (load-scripts.php?c=0&load%5Bchunk_0%5D=jquery-core,jquery-migrate,utils,wp-polyfill-inert,regenerator-runtime,wp-polyfill,wp-hooks&ver=6.2.2:1:82630)