If your Hisense TV is not broken, it is recommended to buy a high-quality set-top box for off-board decoding and memory expansion. U disk or mobile hard disk is inserted in the set-top box, and the memory is enough. In order to avoid being stuck in smart TV after 2 years, it is recommended to check the hardware configuration when buying TV. In my opinion, smart TVs should start with at least 4G memory. However, there are really few TVs with 4 G memory at present.
The automation system of general TV manufacturers is particularly bloated, especially when the system is updated. Because the latest system is equipped with the latest TV hardware, the old smart TV must be difficult to bring up. So, according to this, you can also try to restore the factory-installed hardware upgrade. As you said, the memory of TV is too small. By memory, you should mean storage, which belongs to the hardware level. For example, the original TV is 8G storage, and there are too many applications. If you want to change it to 16G, you need to switch to hardware.
Therefore, the integration scheme of smart TV is not a reasonable scheme. Because the cost of the monitor accounts for almost 90% of the whole machine and its service life is long, it is very unreasonable to eliminate it with the set-top box. The reasonable plan should be not to upgrade the top of the machine. The upgrade of all kinds of software will lead to insufficient memory, and even occupy the storage and running space of the operating system, resulting in failure to start. Pay for the insurance, and find maintenance personnel to reinstall the system.