Exercises/home remedies/advice to help with suspected tendon issues causing chronic pain in lower biceps (near elbow)?

I’m a 50-ish male and looking for advice on gentle exercises, home remedies, or other advice to help with an issue I’ve had for about 5 years at least involving chronic pain in my left lower biceps, basically in the middle of inner arm and a couple inches up from elbow crease -- and to a much, much lesser degree in my right lower biceps when the arm is extended, raised above my head, lifting things etc.

It definitely can flare related to specific physical activities esp. if I haven’t done them for a while and then start up — including swimming, bicycling, and using a rowing machine. I had a really bad flare in June of 2024 and am having a moderate flare now. I think it may also tend to flare worse when I am taking the beta blocker atenolol which I have taken on and off for mild POTS-like issues the last 2 years. But the problem pre-dates use of atenolol and I think use of other beta blockers (I used to be on propanolol) but I think has only badly flared on atenolol.

I haven’t had imaging or really seen any specialists about this at all yet, but it seems almost certainly to be some kind of tendon issue from what I’ve read. I also have history of chronic peroneal tendonitis in one ankle, which may be tied to a bad sprain I had thought that was ten years prior to the condition starting. But I was able to manage the peroneal tendonitis very well with just a video of exercises from a PT I found online that helped reduce the pain and then it went into remission for many years.

I have never particularly injured my biceps, to my knowledge/recollection. I have a history of chronic unexplained muscle pains on and off at times going back to teenage years, including with my upper spine and shoulders (a couple different x-rays 15 years apart suggested I had a somewhat unusually flat upper spinal curve) and it’s possible this with posture ties to biceps tendon even though issues are happening at other end than where people usually have biceps tendon pain in their shoulders.

I haven’t taken any antibiotics of any kind in I think 25 years, just never prescribed. I did have to undergo months of antibiotics about 25 years ago for latent tuberculosis after positive skin test following travel in Asia. But none of this can really be tied to that at all. I have other wacky theories, that are hard to entirely support and that doctors just shrug at, of origins of this issue related to the weird changes in my vasculature that happened at the same time 5 years ago all on the left side of the body in arm, shoulder, and lower leg, same time as POTS-like issues went from barely noticeable to extremely problematic. This could connect to my suspected long COVID or other post-viral syndrome, but the timing of my first noticing this actually seems possibly more connected to my receiving MRNA COVID vaccine (I only get non-MRNA Novavax vaccine now because of other side effect issues), but really I don’t care that much about origins so much as how to get this better.