I graduated with my B.S. during the pandemic and decided to go directly into a non-thesis Masters in Earth Science. I want to pursue a PhD, however I am unsure about my eligibility without having completed a thesis beforehand. I do have some research experience which have resulted in 4 conference posters, although I have not published a manuscript to date. As I prepare for my next steps, I would appreciate any insight. My other consideration is to seek a one year MRes though a school in the UK.
In my experience, having a non-thesis MSc in the UK doesn't really make much difference in terms of PhD applications. If you have a supervisor/tutor who you worked closely with (or at least knows you well enough), and can write you a strong letter of recommendation, you should be fine. Often MSc students' thesis isn't even relevant for the PhD they're applying for anyway. It's also uncommon here to have publications in the sciences before beginning a PhD.
My advice would be to just apply for the PhD's, write about your research experience in your cover letters/CV. If your grades are up to the standard, I don't think you'll have much of a disadvantage .
People have gone from just a BS to having a PhD as well as from programs like OMSCS (example of an online non-thesis MS) to being able to get a PhD so I would imagine it is possible for you as well. I would definitely highlight the research experience that you do have so far, as a PhD is all about your research. Also, I would make sure that you know what your (specific) interests are in, as that will be of great help for identifying programs and advisors of interest, and vice-versa.
I'd start by talking with any research advisors you have had or advisors in your current program to see if a PhD is the logical next step for you, and if you can still get involved in research at your current program to help further hone your interests.