Graz has hotels available for visitors in all budget classes, from youth hostels all the way to luxury hotels.
The Graz Tourism Ofiice offers a dedicated website for conference participants in which you can find a number of hotels (more will be added as the date of the conference draws nearer and contingents become available):
Graz Tourism Booking Platform
(this Booking platform is open till the 19th May 2023)
You can of course also find additional accomodation through other platforms that you are used to.