This is something that I would like to understand without importing the private key for each crypto/fork. The key is 64 carachters long.
With 64 characters it's more likely that your private key is for single coin only, probably Bitcoin, multicoin wallets would usually use seed words instead.
You can first try using Electrum wallet on clean device and importing private key to see what addresses have been used, and if there are any Bitcoin left.
Than you can use services like findmycoins.ninja to see if there are any forked coins leftovers.
I don't know any easy and safe way to check private key for all altcoins.