Godot 4.0 seems terribly slow on Mobile

I, like many others am terribly excited for the upcoming 4.0 release so I've been obviously trying all the alpha versions coming out (these tests were done on RC1), but I seem to get really low fps on Android with the Mobile Renderer, I do acknowledge that my phone is an ancient low end device (it's a xiaomi redmi 7), but it even seems to struggle on simple scenes like this one I've been testing:

In this scene I have a simple environment and a directional light without shadows.
With the visual profiler I can see the gpu uses 11.ms for tonemapping (set in linear in enviroment) and 4.0 ms in shading meshes with the light on (just one with the light off).
With a full mesh covering the screen i get below 55 fps, even with 3d resolution scaled down to 0.35
I first wondered if it was a vulkan device driver problem, so I decided to use Unity to do a quick test and comparison
(used a 2020 version i had before I focused on godot, and I run the scene with Unity Remote) (Ugh, I know) and it seems to run fine with the default Unity URP renderer scene
this one:

running at 250 fps (at least i think so, I tried setting up a label to display 1/delta time and this was the result) with some optimizations like scaled down resolution which I wasnt able to figure out how to disable for a proper comparison.
But the difference between the 2 of them is quite high, is there any setting that I havent figure out how to optimize?
Or is there a way to imitate the default Unity optimization in advance?
Thanks everyone for the time to read this as I do acknowledge this is a long post : )

Megalomaniak
I randomly tweaked all the settings i knew could improve performance and saw a major improvement and now the scene could at least run >60 fps, the settings I changed from default are:
Disabling all filtering from the Textures tab or setting them to nearest,
setting all shadows atlas size to 1024 with no filtering (even tho they do not look acceptable)
setting GI to half resolution even if I dont think this scene uses any form of it?
setting all depth of field to the lowest setting
I skipped environment tab because I dont use its features
I remove screen space roughness limiter
and scaled the resolution by 0,35 (sadly the performance are still not good on its native resolution of 720p
Here's what the visual profiler says:

Next step will be trying if this old scene I and 3 other students had made for a Uni course with Godot 3.3 will run on my device (it used to run at >45 fps on my device without grass and shadows as the whole thing is not bestly optimized)

I've been testing a lot more and I'd like to end with some praise.
On my laptop tests done on what I'd like to define as a "craptop" which features an amd A12 9720P as a processor plus a dedicated graphics card unrecognized by neither windows or linux,
on this scene with a directional light and shadows with a map size of 4096:

I was able to go from 30 fps on godot 3.5.1 (using GLES2 because it performed better than GLES3)
to 90 fps on godot 4.0rc1(Forward renderer)
Sadly the scene was acceptably runnable on my phone only on 3.5.1 achieving a 50 fps without light and shadows ( +light: 30 fps + shadows: ~10fps, no light no grass: >60 fps)
So I can say that beside the bad performances on mobile there is a lot to praise here, also as expected the scene scales infinitely better running ~50 fps with lights and around 2.5 milions quads of alpha scissored grass.
I'd love to see how it performs on my desktop when I have the time.

Back to my 4.1 performance analysis:
at native resolution with mostly optimized settings from default:
even linear tonemapping seems to take ~10ms on my phone which means environments were unusable,
the opaque rendering phase seems to take ~10 fps on a scene with an empty camera and adding a simple quad with default material covering the whole screen adds around 2 ms for each one.
Again this could be just my phone's Adreno 506 GPU acting weird and being low end and old (even tho apparently much more higher end devices seem to struggle a little bit too), but as I said before on Unity vulkan URP renderer MUCH more complex scenes run MUCH more smoothly,
and as low end devices gets better at everyday tasks I can see a lot of the market share steering towards them, plus I get that optimizing for low end and old devices can be a huge hassle for an open source project which tries to provide high visual fidelity on complex scenes it has the benefit of improving how many players our games can reach and it's also quite good for our environment.
Thanks everyone for listening and replying to my long rambling, I hope my test can be useful to detect where to improve and I'll be available to do some more tests or provide my test scenes to anyone who'd like to do more tests with them : ) .
Have a great day!