I was paid by an abroad entity for January-August 2020, and no way to obtain from them Form 1099. How to put this wage in the tax return?

Are you reporting this on Schedule C (your sole proprietorship, also for contractors and consultants)?

If so, in the Business tab, report it as General Income under the Business Income heading. Here you will be able to enter the name and the amount of income for which you have no tax forms.