It appears ODNR is starting to add new Wi-Fi options to some of their parks. We recently stayed at South Bass Island and used the CampFireConnect portal to connect. It worked well, and they should continue rolling this out to more parks in the future. As of writing this article, the following parks offer Wi-Fi.
via ODNR
East Harbor
Grand Lake St. Marys
Hueston Woods (new in 2023)
Indian Lake
Lake Loramie
Mohican
Rocky Fork
South Bass Island