My point is about doing research without PhD as a hobby. Since I would not get paid anyway, I do not see reason to spend a few years, just to get paperwork sorted. Most data are publicly available. Most researchers are very happy for helping hand.

Privately founded research instruments are different topic.

LIGO data are here: https://www.ligo.caltech.edu/page/ligo-data

Xray data are also publicly available, I would suggest skyview https://skyview.gsfc.nasa.gov/current/cgi/query.pl

Requests for Arecibo telescope are here: https://www.naic.edu/ao/scientist-user-portal/proposal-submi...