[Solved] I am unable to install flatpaks as user.

Well, after some very obscure search over internet, I found something that solves my issue (maybe yours too in case you want to install packages as user).

If you use Lubuntu (I don't know whether it works on other distributions), you have to go to the folder /home/[youruser]/.local/share/flatpak/repo/. There is a file there called config. Open it, and write something like this:

`[core]
repo_version=1
mode=bare-user-only
min-free-space-size=500MB

[remote "flathub"]
gpg-verify=true
gpg-verify-summary=true
url=https://dl.flathub.org/repo/
xa.title=Flathub
`

(By the way where it says true, I set it as false, thinking that was my issue).

Now, when I install OBS Studio as user, it lets me.

PS: if GPG verification is set as true, make sure you downloaded the flathub.gpg file from the repo and copied it to your local folder as flathub.trustedkeys.gpg and flathub-beta.trustedkeys.gpg