They have updated this notorious IDA Pro plugin for both IDA Pro 9 and IDA Pro 8.x.
Taken from its GitHub page:
IDA Class Informer plugin for IDA Pro 9 and older versions.
This plugin has been tested with IDA Pro 9.0, and 8.4, both 32-bit and 64-bit versions.
You no longer need a separate version of the plugin for working on 32-bit files in 64-bit IDA from v2.9.
For IDA 9, you just need to install ClassInformer64.dll.
For IDA 8, you need to install both ClassInformer_IDA8x64.dll and ClassInformer_IDA8x.dll.
If you have both IDA 8 and 9 on your machine, copy them to the IDA's directories according to the versions, or copy all dlls into %IDAUSR%\plugins.