By registering get_post_meta (ID); get all the meta fields.
https://wp-kama.ru/function/get_post_meta
Using
$ meta_values = get_post_meta ($ post_id, [$ key, [$ single]]); $ post_id (number) (mandatory) Post ID, arbitrary fields of which need to be obtained. Default: none $ key (string) The name of an arbitrary field whose value you want to get. If you leave the field empty, all arbitrary fields of the post will be received . Default: '' $ single (logical) true - returns the value of the meta field (if there are several fields, it will return the value of the first meta field). false - returns an array of all values of meta fields with the specified key.
If a serialized array is in the value of an arbitrary field, then true will return a normal array, and if you specify false, then an array in the [0] element of which the same serialized array will be returned. Default: false
Accordingly, by running all the goods on this page and getting all the meta fields of each, by iterating through all the fields of each, we find what values it has, add to the selection, if not yet added. Then, by sampling, we display only those that were encountered.