China already has an (uncompetitive) alternative stack, covering silicon to operating system.
The problem is with building a competitive stack, Huawei can't get access to a 7nm fab in China, nor is their talent skilled in working with the limitations of said newer process, which kneecaps their ability to build chips competitive with Qualcomm and Apple.
Huawei can build 7nm chips at TSMC, but due to their ARM license revocation and Qualcomm's inability to license them cellular patents under FRAND during this dispute, TSMC is unlikely to fab IP infringing chips.
If TSMC were to fab these chips, their other 7nm clients (primarily Apple, followed by ARM licensees Qualcomm & AMD (which uses ARM TrustZone)) would all be in an uproar as ARM would likely prohibit the use of their designs at TSMC fabs.
Wrt China building their own 7nm fab, it is very unlikely they will get it off the ground in the next few years. Only TSMC & Samsung have succeeded in this, Intel, Global Foundries (formerly AMD) and many others have spent tens of billions and half a decade trying to build better than 14nm processes to no avail.