it’s all relative. In android and iOS, the need for strong sandboxing is vital because the users are installing shitty user-hostile apps next to their banking apps by default. In android’s case, google wishes to protect its own access to your data as well as stop bad apps from going to town on your device.
But In the linux context, you might have only one bad app - probably the browser since it is running anything you put through it. Also, there is no google trying to lock your data in for its own purposes. If your other apps are just open source types (gimp, vlc, libre office) installed from a debian repo or whatever, then I’m not sure sandboxing is quite as critical.
There are also some sand boxing methods in linux, and if you wanted to go far with it, you could spin up VMs or containers à la qubes OS.
The reason linux is secure on servers, is that it only runs the minimum of what it has to. ‘Apps’ aren’t the issue - more likely protecting access to RAM from processes and segregating network access.
So if your linux box is basically a browser and a few open source apps, then who really cares about in-depth sandboxing? It’s not like you will be installing spyware that easily on linux anyway and your attack surface is probably very much reduced in comparison to a similar windows machine.