You need a template for the cell, in src/argus_htmx/templates/htmx/incidents/_incident_ack_by_group.html
:
{% load argus_htmx %} {% if incident|is_acked_by:column.context.group %}X{% endif %}
You also need to add the column to the column config:
INCIDENT_TABLE_COLUMNS = [ .. IncidentTableColumn( "mygroup_ack", "MYGROUP", "htmx/incidents/_incident_ack_by_group.html", context={"group": "MYGROUP"}, ) .. ]