In the UK there is a large, ongoing clinical trial called 'RECOVER' to test different COVID treaments for hospitalised COVID patients. One of the trials included giving hospitalised patients aspirin. The trial was not looking at the treatment of long-covid symptoms (at least not directly in hospital patients).
"A total of 7351 patients were randomised to aspirin 150 mg once daily and compared with 7541 patients randomised to usual care alone. There was no evidence that aspirin treatment reduced mortality."
Link: RECOVERY trial finds aspirin does not improve survival for patients hospitalised with COVID-19: https://www.recoverytrial.net/news/recovery-trial-finds-aspi...