There are no direct buses between Savonlinna and Kuopio. The Matkahuolto search engine is not very good with connections involving transfers and you can get more results by splitting your search, if you know where to transfer.
In this case you can get more options by searching for two separate legs: Savonlinna - Juva ABC and Juva ABC - Kuopio. Juva ABC is a large service station located in the interchange of highways 5 and 14 (also known as Vehmaa interchange, that's why the search engine translates it to Vehmaa th), so even though you might have a long wait there, you can spend it at the service station (and have even lunch etc. there if you choose to). Note that at Juva ABC you would also have to change stops when transferring: the bus from Savonlinna would drop you off at highway 5 southbound and the bus to Kuopio would depart from the northbound stop. The interchange is under major roadworks right now because highway 5 is being built to dual carriageway, but the bus stops are still there.
Matkahuolto is not a bus operator itself. It provides services to most bus operators and the timetable search on their website lists practically all buses outside of the largest cities.
Anyhow after all Savonlinna is a small city, so it doesn't have much connections (especially as coach travel has not yet recovered from Covid) and there will be very limited options.
Thank you for the reply!