We are migrating from bs3 to bs5. After a day of research and tries, finally I've got an working solution.

This answer helped me to implement x-editable with bs5: https://github.com/wenzhixin/bootstrap-table/issues/6034#issuecomment-1189563176.

So, process is, as follows:

1. Remove old x-editable CSS and JS links.
2. Import new files: https://raw.githubusercontent.com/skycyclone/x-editable/refs/heads/develop/dist/bootstrap5-editable/css/bootstrap-editable.css and https://raw.githubusercontent.com/skycyclone/x-editable/refs/heads/develop/dist/bootstrap5-editable/js/bootstrap-editable.js.
3. Import icons images from: https://github.com/skycyclone/x-editable/tree/develop/dist/bootstrap5-editable/img.
4. To display 'Approve' and 'Cancel' buttons correctrly in popover I've also needed to import Font Awesome icons from: https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.7.2/css/all.min.css. This, may be optional in your case.