There are a few ways to access free journals or obtain fee waivers for low-income countries:
Open Access journals: Many scientific journals offer open access options, which means that the articles are freely available to the public. Search for "open access journals" in your field to find these resources.
Library subscriptions: Check with your local library to see if they have subscriptions to scientific journals that you need. They may have access to a large number of journals and can provide you with free access.
HINARI program: HINARI is a program that provides free or low-cost access to a large number of scientific journals for researchers in low-income countries.
Journal fee waivers: Some scientific journals offer fee waivers or discounts for authors from low-income countries. Contact the journal directly to inquire about these options.
Pre-print servers: Pre-print servers are websites that allow researchers to post their research findings prior to publication. Many of these pre-prints are available for free.
Rodolfo has given nice options. You may also email the author(s) or message them via Researchgate to request a full-text or pre-print. Who knows, you'll get to network with them as well.