No it's noty possible : planning must respect WBS structure, so filtering and sorting is not possible.

I don't understand your answer. Any user with data restriction on Projects, will only see his projects on the Gant view. So, filters are applied and there is no impact on WBS.
It would be usefull to filter by client or status on the Gantt view.

Imagine WBS stucture
1. A_xx
1.1 B_xx
1.2 C_yy
2. D_yy
2.1 E_yy
2.2 F_xx
2.2.1 G_yy

Image I filter on all projets with name containing "yy"
I should show
1.2 C_yy
2. D_yy
2.1 E_yy
2.2.1 G_yy
I cannot show correct WBS structure, it's a real mess !

So yes you can select one project, then show it's whole content.
For instance select A_xx will show
1. A_xx
1.1 B_xx
1.2 C_yy
or select E_yy will show
2.2 F_xx
2.2.1 G_yy
so WBS strucutre is correct.

That's why it's not possible to filter nor sort on Gantt view.

But this is the case : in the printscreen, I see my Gantt view only on my project; as you say, the WBS is a mess but this not an issue.

No it's not what you get
You get complete structure from a given starting point.

What whould be a real mess is display

1 A
1.1.1.5 B
1.2 C
1.2.4.5.1 D
2.2 E
2.3 F

I would not know how to display it
A
___ B
_ C
_____ D
_ E
_ F
E and F would seem part of A, and summury bar are then impossible to draw

In fact, real structure is
A
_ X
___ X
____ X
____ X
____ X
____ X
____ B
_ C
__ X
__ X
__ X
__ X
___ X
___ X
___ X
___ X
___ X
_____ D
X
_ X
2.2 E
2.3 F