how about doing还是 to do

肯定是 how about doing，绝对没有 how about to do 的，因为 about 本身属介词，介词后面要加名词或者动词ing 形式。
how about doing = what about doing 意译为“做某事怎么样”，表向对方提出的建议。

doing
how about/what about doing sth？
做某事怎么样？

about 这里是介词，更具介词后接宾语，所以应该是doing

how about doing
about 后面跟名词。。。。所以用doing

how about doing

做某事怎麼样？

Doing