Crowne Plaza Hotel, Downtown Dayton. https://www.cpdayton.com/ I don't plan on staying there again since I live only 30 minutes from Dayton/Xenia , but I have always enjoyed the festivities.
Went to the 2019 show at Greene County Fairgrounds. They refused to open up the parking areas overnight for camping. I was willing to pay extra but they said NO even though I had a self contained cab over truck camper (no hook-ups needed). All RV parks and state parks were full. I ended up staying at a church parking lot in another city and payed them a $20 donation (unsolicited). Forget staying at a hotel nearby. They are all reserved. Your bet bet is to contact the committee leadership of the Hamvention online. They will probably have the info you need.
Hotels are already booked for the May 2022 hamfest? I am a stay at hotel person not camping and no RV - would be flying into Dayton.
I just called some hotels in the area. They don't even take reservations a year in advance. I did find a hidden gem newer hotel very close to the fairgrounds. Had a very nice chat with a manager. Their system currently won't let them book reservations beyond 12/31/2021. I want to book it first when I can before suggesting it to get ahead of the crowds