Publishing short and simple results I have a manuscript that has been conference-rejected 3 times up to this point.
Just to clear things up, I am by no means a senior researcher but I am not a junior who cannot judge the strength of my own work either (I have published in some top conferences such as STOC, PODC, etc.). For this manuscript, I haven't submitted it to any venue that is clearly inappropriate with respect to its strength.
In particular, what usually happened was that I get a mix of accept/weak-accept/weak-reject. Even in the reviews that recommended a rejection, they said the paper was decent (my point is that I did not submit a junk paper!). In general, even though I disagree with some of the reviews, I respect the PC's decision.
Now, I don't want to keep submitting it to conferences because while the paper is publishable, it usually does not fall into the top percentage of conferences' acceptance allocation. It will keep wasting people's time (i.e., reviewing). Improving the paper is also unclear because I have matching upper and lower bounds.
I have someone suggest submission to Information Processing Letters since they sort of accept short and simple contributions. I wonder if there is any alternative since I don't really like the idea of publishing with Elsevier.
There are two natural strategies:

Put it on the arxiv, forget about publishing it somewhere else. I have several such writeups - people see them and cite them.

Go to lower venue conferences. Don't give up. I had a paper rejected 5 times before it got accepted, and it was a strong result that later appeared in a good journal. Rejection is just acceptance to the complement, etc.