No problem, and thanks for making your goal a bit clearer.
I wouldn’t use the Digitakt for this purpose and especially wouldn’t deal with the MIDI loopback stuff if you’re still discovering the Digitakt.
I am not at all familiar with Linux so I’m not sure what software instruments are going to work with that OS, but I think getting a fairly cheap digital piano is going to be much more immediate and fun for your purposes. Here’s a pretty good guide for some options. Depending on where you are, there should be plenty of used options on Craigslist as well, as many people tried playing piano during the pandemic and quickly gave up. I personally like the Yamaha P-115 quite a bit but its a bit pricey.
As you progress, you can use the Digitakt to add beats and rhythms to your playing, so I’d definitely hold onto it as you make your way in your music journey. Good luck!