The bill of attainder argument is therefore exceedingly weak, and more or less guaranteed to fail. The only reason it isn’t frivolous is that various Baby Bells challenged the 1996 Telecommunications Act as a bill of attainder, and one federal district court actually agreed with them. That decision was overturned on appeal, and other courts also rejected the argument.
Huawei’s second legal argument is that Section 889 violates due process of law. It isn’t very specific about why, but the complaint does say that Huawei was deprived of its “opportunity to be heard.”
The problem with this theory is that there’s no due process right to be heard by Congress before it passes a law affecting you. Congress isn’t a court that must give you notice and a chance to be heard before affecting your property rights.