This is going to ruin ARM. The company is already struggling to generate growth. Its dominance of the mobile space is so complete that there's simply no more marketshare to capture. That's why Softbank had wanted to offload it to NVidia. With these restrictions taking a big bite out of potential growth, the company is going to be under a lot of pressure from shareholders to generate returns by cutting R&D and gouging licensees.
Meanwhile, Chinese-backed firms will be poaching their engineering talent. These won't enjoy merely implicit state support, but will also have a captive market. No worry about competing with Team Blue and Team Red's latest and greatest. Guaranteed success, basically. Any British engineer jumping ship is guaranteed to become a multimillionaire. Would he refrain from doing so--not for King and Country--but Uncle Sam?