Profile: enma

Problem:
A select custom field is used as a Views filter but shown as checkboxes so that more than one option can be selected, but the View results do not work as expected.

Solution:
You need to modify the query arguments with the wpv_filter_query hook before the query is run.

Supporter provides sample code here (https://toolset.com/forums/topic/filtering-content-by-checkboxes-selection-2/#post-1101628) and the final version used by the client is shared here (https://toolset.com/forums/topic/filtering-content-by-checkboxes-selection-2/#post-1101696)

Relevant Documentation:
https://wp-types.com/documentation/programmer-reference/views-filters/#wpv_filter_query