Hi creator of MineOS here,
Profiles are a convenient way for you to add/change what server software runs for each of your Minecraft servers.
As an example, there are the Mojang official jars, where a profile consists of a single Java jar file. There are also well-known third-party packs, like Feed the Beast, which are collections of files all zipped up. The job of a profile is to–once downloaded–just get copied (and extracted if necessary) to the server’s directory on the filesystem.
In that way, a profile is entirely optional. If your imported server already has a jarfile included, then that file is also something you can immediately go and select for MineOS to run.
Now, if none of this seems to make sense, one explanation might be that you aren’t using the most modern MineOS version. There are multiple versions of installable MineOS, one has a webui written in NodeJS and the other in Python.
Since you said you installed it on a Debian system, I guess that means you followed the instructions from the wiki. If you did, ensure you followed this:
If these instructions aren’t what you followed, I recommend you clear out what you’ve done so far and then use these instructions. Profiles were handled differently in Python (and they were clunkier and less intuitive). Now, they’re as simple as clicking “Download” and selecting it from a dropdown.