I'm trying to install the latest ada_language_server:

$ alr get ada_language_server=23
⚠ Complete solution not found after 5 seconds.
ⓘ The best incomplete solution yet is:

RELEASE DEPENDENCY
(none) gnat((>=12 & <=2000) & (/=2020)) & (>=11) (hinted)
gnatcoll=23.0.0 gnatcoll((23.0.0) & (^23)) & (~23.0.0) (solved)
...

The gnat dependency is not resolved, even though gnat 12 is available:
$ alr toolchain
CRATE VERSION STATUS NOTES
gprbuild 21.0.2 Available
gprbuild 22.0.1 Available
gprbuild 2022.0.0 Available Provided by system package: gprbuild
gnat_native 11.2.3 Available
gnat_native 12.1.2 Available
gnat_external 11.3.0 Default Detected at /usr/bin/gnat

Since I've selected gnat_external 11.3 as the default, perhaps it is ok that ada_language_server cannot be installed. But in that case, the error message should be much clearer. Currently, it just keeps asking for more time to find a solution, but it will never succeed. Perhaps the error message could be:

"The default toolchain gnat_external 11.3.0 does not satisfy the ada_language_server gnat dependency. To resolve this, select a different toolchain".

I'd prefer alr to offer to use gnat 12 for just this crate, or perhaps an option to specify that.