There are several longitudinal studies looking at PASC, in which biopsies from the gut ( and other parts of the body ) show large quantities of viral debris/spike protein triggering chronic inflammation and mast cell activation. In some cases the debris is persisting for 2+ yrs after infection. The chronic inflammatory state ( and histamine release ) causes a shift in the gut biome which then leads to multiple GI symptoms and has potential for causing disease eg. inflammatory bowel disease, IBS, Coeliac disease and even cancers.One of the theories is that covid hides is in the gut bacteria.
Interestingly some people are doing those gut bacteria tests and finding one or more bacteria as totally gone. They are using probiotics to try and repopulate that area.
I know gradually over the 2 years since I got covid my digestion went downhill.