这个英文句子究竟是什么从句?It was by no means obvious how it would be use

这句话是主语从句.以IT 为形式主语,可以倒过来,how it would be used was obvious by no means.
it +be obvious ,true ,likely,certain,good +that 从句是主语从句中一个典型的句式.此举中应该是省略了that.
而且不是说所有的从句都要有that,how 就不可以作为连接副词了.在宾语从句中就有以HOW引导的宾语从句.如：Could you please tell me how you read the new panel?