NAC ( N-acetyl cysteine) is a good expectorant to try, if you can get it. There are also lots of other supplements and herbal treatments that can be beneficial, such as dandelion leaf tea. Another avenue to look into could be gut bacteria, this interacts very closely with your immune system and an imbalance in your gut bacteria can be the root cause of many ailments, Dr Sabine Hazan has done a lot of work on this, including for COVID, parkinsons, autism, etc. It will be interesting when eventually, maybe in another 30 years, Dr Wakefield will effectively be shown to be right about the gut health link to autism that got him fucking obliterated by big pharma decades ago. The rot goes so deep that there really doesn't seem to be an end to it.