You can download in whatever format is available for any given movie. Often movies are available in multiple formats, especially the popular ones. DM your email address amd I can invite you to a private tracker but only if you promise to keep a good ratio.

Also I’m sure some other commenter is literally going to say “mkv is a container not a format” but whatever, if you want mkvs the movie or show you want has to have an mkv available.