From the Views Date Format SQL project page:
The Views Date Format SQL module allows to format date fields using
SQL. This enables group aggregation for date fields using the choosen
The core functionality is to remove the date formatting from render()
and put it in query(). I.e. format date values using SQL's DATE_FORMAT
rather than PHP's format_date. This is achieved by assigning a new
default handler to node 'created' and 'changed' date fields. This
handler extends and overrides views's built in
After a review of the module, you'll see that this new default handler is "views_date_format_sql_field".
As far as how this is being used on your site, you'll need to figure that out for yourself. I'd start by reviewing the views that get disabled when you would uninstall the module - check for any timestamp fields, e.g. 'created' or 'changed'. The fastest way might be to scan the config files for "views_date_format_sql_field", the new default handler the module adds. Once you know where the module is being used, you can determine what effect removing it would have.
Alternatively, it may be simpler to make the module D9 compatible. Many Drupal 8 modules are Drupal 9 compatible after a simple change to their .info.yml file - replacing
core: 8.x with
core_version_requirement: ^8 || ^9.