"That’s not argumentative by the way just genuinely I don’t know how to take that."
Sure, I understand.
You can look up a long list of mystery immune conditions, and see over and over that "the cause is unknown". The immune system is not well understood yet. No one can rule out an inflammatory cause.
Or I could say, 'what were your test results for TNFa and IL-23'? Which you probably weren't tested for, as a shot in the dark. Or any number of other IL's, and there are many.
Also a btw: I have said that autoimmune (which requires autoantibodies or auto reactive T-cells) is not the same as autoinflammatory, which uses biochemical signalling molecules. If a person eats a peanut and dies, their immune system killed them, but there was nothing autoimmune. Or another person's skin might erupt from the sun, because of an immune reaction, though there is no allergy-molecule involved.
There is even another called "immune mediated".
"but what would the next step for investigating that be after everyone I’ve already seen?"
You can try fixing the gut problem, then seeing if everything else subsides. The way that gut inflammation can drive many bad conditions such as RA and lupus and ankylosing spondylitis and on and on is more and more being looked into - as first stages of investigation.
More and more, there is evidence of gut inflammation being linked to many other inflammatory conditions like rheumatoid arthritis and lupus. The gut might cause or exacerbate the other condition, and/or vice versa. Or a third, other inflammatory thing might be the underlying cause of it all.
So then why couldn't the gut also influence inflammatory nodes anywhere, right? That's especially for those who are predisposed to inflammation. I think I'd said this to you some time ago... eliminate the underlying driving force and the nodes could stop multiplying.
Yes, antibiotics can be a real gut problem. Especially for some people.
You can try sublingual methylated B12, to see what happens and how you feel.
"However I’m assuming that with lymphoma the symptoms would only get worse not go away over time."
Yes, most likely true. But inflammatory conditions are known for flare ups.
"I thought it was worth mentioning."
Yep, it certainly is.
But is it lymphoma? Not much chance of that.