I am a US citizen. I live abroad and am enrolled in a PhD program at a foreign university, for which I receive ~20kUSD/year.
I will refer to the money received from the university non-specifically as income because
the university is in a non-English speaking country and its English language documents are sparse and inconsistent
what type of income these payments constitute is central to my question:
Since my tax home is abroad and I pass both the bona fide residency and physical presence tests, I am eligible for Foreign Earned Income Exclusion (FEIE). Does FEIE apply to my income?
I would argue that the answer is yes. I am also clearly biased, so I would be grateful if someone with experience in law and taxes could check my arguments.
For FEIE purposes, the payments are either salary or scholarship/fellowships (no other categories discussed in  remotely apply). The former are clearly covered by FEIE. Hence, let us assume the worst case that the payments are scholarships, for which I found
“Scholarships and fellowships fall into earned income, unearned income, or partly into both” 
FEIE applies to earned income, and not to the latter. Quoting further,
“Any portion of a scholarship or fellowship grant that is paid to you for teaching, research, or other services is considered earned income.” 
I have transcripts showing that I receive 90% of the required PhD program credits for “Research credits”, which I spend in a laboratory working for the laboratory/research group, and 10% for mandatory seminars. However, I have no paperwork from the university that actually spells out what I get paid for.
PS: Further information that I do not think is relevant but I might be wrong: (1) For the purposes of local laws, the university is my employer. (2) The payments are taxed locally, no double taxation agreement is in place.
PPS: The internet seems mixed about this. I didn’t find any source that is remotely specific enough to serve as a reliable reference and obviously random people saying random things on the internet except stackexchange isn’t worth much, but here we go:
“A foreign student can include this type of income as foreign earned income, thus making it eligible for the Foreign Earned Income Exclusion (FEIE)” –SusanY1, Intuit Tax Expert.
“Fellowships and scholarships are not considered wages or earned income, and as such, are not excludable under the Foreign Earned Income Exclusion on the U.S. tax return.”  –SusanY1, Intuit Tax Expert
“Scholarship income is considered earned income and it is permitted to be excluded as part of the Foreign Earned Income Exclusion (FEIE) as long as all of the other qualifications are met for the exclusion”  –Susan Y1, Intuit Tax Expert (“all the other qualifications” are not specified but I assume tax home and residency tests are meant here)
“The OP may qualify for the foreign earned income exclusion, which can be used to then exclude her (presumably otherwise taxable) scholarship from her US taxable income. My wife did her PhD in the UK and this is how we treated her scholarship grant, so we ended up paying no US tax on it."  --politicfool
 Publication 54 (2020), Tax Guide for U.S. Citizens and Resident Aliens Abroad (https://www.irs.gov/publications/p54)