Abderrahim Kitouni has announced that the first beta version (3.37.90) of GNOME 3.38 is now available for testing.

GNOME 3.37.90 released

Hi,

GNOME 3.37.90 is now available. This is the first beta release towards
3.38. It also marks the start of the UI, feature and API freezes
(collectively known as The Freeze). The corresponding flatpak runtimes
have been published to Flathub beta.

If you'd like to target the GNOME 3.36 platform, this is the best time
to start testing your apps or extensions. You can use the 3.38beta
branch of the flatpak runtimes.

A virtual machine image is available at

https://gnome-build-meta.s3.amazonaws.com/3.37.90.1/disk.img.xz

It can be used to test the new version, and test/port GNOME Shell
extensions. It is recommended to use the nightly version of GNOME
Boxes to run it (the beta version should be soon available on Flathub
beta, and can be used as well).

If you want to compile GNOME 3.37.90 yourself, you can use the
official BuildStream project snapshot:

https://download.gnome.org/teams/releng/3.37.90/gnome-3.37.90.tar.xz

The list of updated modules and changes is available here:

https://download.gnome.org/core/3.37/3.37.90/NEWS

The source packages are available here:

https://download.gnome.org/core/3.37/3.37.90/sources/

WARNING!
--------
This release is a snapshot of development code. Although it is
buildable and usable, it is primarily intended for testing and hacking
purposes. GNOME uses odd minor version numbers to indicate development
status.

For more information about 3.38, the full schedule, the official module
lists and the proposed module lists, please see our 3.37 wiki page:

https://www.gnome.org/start/unstable

Cheers,
Abderrahim