If I understand your question correctly, you want to display all the options from a multi-selection column as a dropdown select, right?
In that case:
<select name="type" form="form_id" onChange="this.form.submit()"><option value="show-all">Show All</option>{% set types = hubdb_table_column([TABLE ID], [COLUMN NAME]).options %}{% for choice in types %}{% set type_list = type_list~choice.id|list %}{% if choice.id == request.query_dict.[COLUMN NAME] %}<option selected="selected" value="{{ choice.id }}">{{ choice.name }}</option>{% else %}<option value="{{ choice.id }}">{{ choice.name }}</option>{% endif %}{% endfor %}</select>
You can find more info here: GitHub - HubSpot/cms-custom-objects-example · GitHub
You’d also need the logic to handle the query parameters (detailed in the above link) so that the page loads the correct information based on the selected filter.