WP-admin blank page problem

hi everyone,
few days ago wp-admin area started giving me blank page. Console displays this message: The character encoding of the HTML document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. The character encoding of the page must be declared in the document or in the transfer protocol.

Tried disabling plugins one by one, disabling theme, even found that someone managed to fix it by uploading wp-includes from fresh copy of wp install, checked for blank spaces in wp-config… basically tried everything i found as advice on this forum.
None of these things helped, problem still remains. Any ideas how to solve this?