Edit: I encode to/with(?) the codec h246. This question is about containers/filename extensions.

I am digitizing old video mediums, such as VHS, VHS-C and Mini DV. A few colleagues have asked me to do it for them, which is awesome and feels great. Now, for personal use, I encode save video with the .mkv container out of habit. I have no idea why that is bad or good. However, the question is, which container should I use to ensure maximum compatibility with my colleagues’ phones, computers, possibly TVs? Is, for instance, .mpeg the way to go?