There are a number of studies suggesting that covid vaccines may improve long covid symptoms. Here is one such study: https://pmc.ncbi.nlm.nih.gov/articles/PMC9146071/#%3A%7E%3Atext=There+was+considerable+individual+variation%2Clong+COVID+patients%2C+on+average.
So while I'm not sure it counts as an approved treatment, it sure seems like it's worth trying (if you haven't already).
I feel pretty comfortable recommending that people get the covid vaccine.