I’m very new on Linux and i’m trying to get some help.

I tried Linux mint and other debian distros, and since i dont have the sufficient skill to manage linux, this time i’m choosing Kubuntu because of the KDE environment , which i like a lot.

I know more about linux mint and kinda know how to work with him, but kubuntu never tried and i will try this time… but i have some questions if someone can help me.

Kubuntu is ok for a new person on linux?

I want to install apps/programms via flatpak, since this looks more easily for a newbie as me and because of the sandbox, which seems is good (?).

On Kubuntu, is easily to install flatpak via diskover? I see i need to add the flathub repo, but my question is if someone have getting any error or problem with this, or if this is easy to do it.

Other question I have, is about some apps i want to install if i dont find it or just find it on github or something similar. I find an app that really like but this app dont appear in any store, and this app is only available on github via flatpak and .deb . In this case, since the app is not available on flathub or diskover, or via command lines (like sudo apt install firefox - if you understand me) , how can i check this is not a virus or can do bad things on my linux? I use total virus for this, and the checks gives zero flags, but would like to know if for example, i install this programm via flatpak, can break my system.

Other question is about flatpaks from flathub. I know flatpak usually dont follow the theme of my DE. Which is the best way these flatpaks have the same theme as my DE? Is using the flatseal? Any tip about this?

And, btw, if you can give me some tips and advice as linux/kubuntu newbie, it would be amazing for my journey. Cheers all!