Calibre makes converting epubs and loading them onto Kindles. It handles a wide range of different ebook formats. I probably would work with your Kobo as well if you have some non-epub source documuments.
The biggest downside of Kobo for me has been Rakuten's update cadence. The system updates opt-out doesn't actually work from what I can tell and my device only comes out of airplane mode once every few months. Every damn time I do so it has to download an update, lagging out for a long time, and changing the UI in exciting new ways.
Works perfectly.
I don't want to send a copy of "And the Band Played On" (for example) and start getting Chick Tracts.
Calibre is king, set things right and you can just email books to your Kindle.