Simply "Inventory Connector (Filtered)" is missing unable to identify any alternative.

MCVer: 1.21.4
Fabric

Not sure what else is required. All guides/info point to a (filtered) version of the connector but i do not see this as an option.

You don't need a special version anymore. You have to right click the normal inventory connector with the inventory configurator to open the filtering menu (You can also filter individual inventories with the inventory connector by right clicking with the configurator on the inventory).