Since iLinux is based on Unmodified Debian Stable, if Debian will support it, yes.

iLinux OS 2 is based on Debian 10 Stable.

iLinux OS 3 will be based on Debian 11 Stable.

Even though iLinux does not use Gnome as it's Desktop Environment, it has compatibility with Gnome Applications and has some of them pre-installed.

But if a user installs though flatpak, wouldn’t it look weird out of all other GTK apps?

As you know, in Linux there is a wide diversity of Interface Software Layers that Applications use to be displayed: GTK 2, GTK 3, GTK 4, QT, Gnome, etc.

Unfortunately there is no common Visual Consistency Agreement between all of them, so developers have no choice if they want to support all of them in their Linux Distributions.

The only thing developers can do, and that's what we have done too, is to create Interface Themes that display Apps of all Interface Software Layers as consistent as possible.