qGo is able to load files in the MGT format. This format is used by the common editor WinMGT.
The newer WinMGT versions save files with the extension .mgt, but the file format follows the SGF specification, so reading those is just like reading SGF files.
But there are some very old games out on the web in an older format. qGo is able to convert this format to SGF automatically when loading those files.