Services like https://replit.com provide an important need for those who are forced to use iPads to code, but they are not sufficient to learn Linux, or even to learn to really code on Linux using modern methods that depend on containers. Why? Here are some reasons:
That last reason is the most important. Even though you are running Linux from a container spun up on their servers and every key stroke you make into their terminal emulator is directly sent to that servers terminal handler, at the end of the day, it’s not real. Having a sandbox might be nice if you have no access to a server of your own remotely, but there is no value beyond this trivial need. To learn enough to even call yourself a beginner you have to have a real Linux system on a computer you control.