Which @angular/* package(s) are the source of the bug?

upgrade, core

Is this a regression?

No

Description

Trying to get rid of zone.js from our hybrid app (Angular 19 & AngularJs 1.8) but looks like change detection doesn't get trigger for downgraded components even when using signals inside them.
Is zoneless officially support for hybrid app setup?

Please provide a link to a minimal reproduction of the bug

https://stackblitz.com/edit/stackblitz-starters-mitowsjd?file=src%2Fmain.ts

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 19.2.0
Node: 20.19.1
Package Manager: npm 10.8.2
OS: linux x64

Angular: 19.2.0
... animations, build, cli, common, compiler, compiler-cli, core
... forms, platform-browser, router

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.1902.0
@angular-devkit/core         19.2.0
@angular-devkit/schematics   19.2.0
@angular/upgrade             19.2.12
@schematics/angular          19.2.0
rxjs                         7.8.1
typescript                   5.8.2

Anything else?

if i'm missing any setup config please provide correct changes, i find very less documentation or support for hybrid app setups.
And those which are present not updated for while.

Thanks for providing amazing new features :)