There is no such thing as scientific truth? Absolute Rubbish. According to you then you can not prove your own existence by science. Subjectivist codswallop.
Please. Don't make yourself angry over definitions of words like "truth".
The word "truth" is not normally used in science.
That's in part because the entire scientific enterprise begins with an unprovable assumption called "methodological naturalism", which means science can only seek physical causes for physical events.
So the various categories of science begin with observations, or data, which when repeatedly confirmed are called "facts" (not "truth").
Data can be related by mathematical "laws" (not "truth"), and attempts to explain how and why are called "hypotheses" or sometimes "educated guesses".
A scientific hypothesis which can be confirmed by making valid predictions is called a "theory" (not "truth").
So the word "truth" is, or at least should be, reserved for higher level discussions -- of metaphysical, supernatural, religious, ethical, aesthetical, etc. matters.
As for your obvious alarm over some alleged "subjectivist" notion, I don't see that at all.
My existence is not a matter of "proof", but rather is confirmed as a fact by daily, hourly, even moment by moment observations.
Those are all matters of definitions of scientific words, of which higher "truth" is not normally one.