Can a reference list for a research paper contains references for resources that are never cited in the text but was useful for the research?
No, it can't. This is actually checked during the proofreading step and you are asked to remove all items from the reference list that have not been cited in the text. That is actually pretty common to happen (as is the opposite of missing items in the reference list) since it's easy for citations and reference list to be out of sync if you don't use a reference manager and have a lot of revisions.
I think it's technically ok, but It's defininitely bad style. How was it useful and yet not worth refering to in your manuscript? It also leaves unclear which part of your research it supported.
Elsevier e.g. actually state in their author guidelines that cited references must be mentioned in the text and vice versa: https://www.elsevier.com/journals/learning-and-instruction/0959-4752/guide-for-authors#68000