Yes, It' not supported for Horizon HTML Access for now as SurajRoy shared, and there is no plan to support it in near future.
We have other Horizon Clients running on different platforms that can support SmartCard redirection for remote apps inside VDI, please check the docs accordingly.

If there is any blocker for using other Horizon Clients, and SmartCard with Horizon HTML Access must be used in the setup, please reach the support/sales team to get further assistants.