Loongson's newer processors use 28nm and under nodes and Moore Threads use 12nm.
Those processors are made using American, Japanese and Dutch equipment. Therefore they cannot supply Huawei and are vulnerable to sanction.
Huawei cannot work with Longsoon or Moore Threads. Huawei cannot work with any well known domestic architecture. Huawei also cannot work with SMIC because that company's production lines use Dutch and Japanese equipment. What you need is the following: All Chinese equipment including lithography machines (Currently such production lines do not exist for mass production, as far as I know). All Chinese CPU architecture and IP (Must be manufactured on 90nm and lower). All Chinese software ecosystem to support it (Still in infancy, not sure if Chinese OS can take off). And you need it to be competitive in terms of performance. This day has been known and coming since 2020. The mountain is extremely high to climb. It can be climbed, but it will take a long time and the question is whether the will exists. It might be easier for China to pursue leapfrog technologies instead.