It's possible to install a Greek keyboard on a desktop computer as well; https://www.duolingo.com/comment/17706271 has some links.
That doesn't change your keycaps, but the layout is similar enough for most letters that you can either get used to it fairly quickly, or you can mod your keyboard with a marker or stickers to add the Greek letters as a reminder.
You can check out this discussion here https://www.duolingo.com/comment/17706271
(Please make sure to always check the Discussion section of the course. This is a topic we get a lot of reports for, although there is almost a gazillion of comments and discussions that include all the links. ^.^)
Happy learning! ^.^