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After further investigation, I found that the igxFilterCellTemplate does not exist in Ignite UI for Angular 6.x.x. This feature has been introduce in IgniteUI for Angular 7.2.3 as stated in our changelog.
Please note that according to our support policy support is applicable to two versions back - latest stable, and the previous major version. Having this in mind version 6.x.x can be considered retired. In order to take advantage of all new features and functionalities would I suggest updating to Ignite UI for Angular 10.1.7, which currently is the latest available. For more information, you can refer to our official Update guide.
Please let me know if you have any further questions.
Best Regards, Martin Evtimov Entry Level Software Developer Infragistics, Inc.
I am glad that you find Martin`s suggestion helpful!
Thank you for choosing Infragistics components.