SPFx ApplicationCustomizer script not loading in MS Teams tabs (List or Library)

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint Framework

Developer environment

None

What browser(s) / client(s) have you tested

• 💥 Internet Explorer
• 💥 Microsoft Edge
• 💥 Google Chrome
• 💥 FireFox
• 💥 Safari
• mobile (iOS/iPadOS)
• mobile (Android)
• not applicable
• other (enter in the "Additional environment details" area below)

Additional environment details

• browser version 126.0.6478.127 (Official Build) (64-bit)
• SPFx version: 1.19.0
• Node.js version: v18.17.1
• MS Teams: 24152.412.2958.9166 (The client version is 49/24053101421.)

Describe the bug / error

After creating a new SharePoint tab in Microsoft Teams and selecting any existing list or library from the SharePoint site, the ApplicationCustomizer scripts are no longer loaded. This functionality was working a few days ago.

Steps to reproduce

1. Create a new SPFX Application Customizer using the Yeoman Generator. By default, it should show an alert on each page.

2. Build and package the solution with the --ship option, then upload the '.sppkg' file to SharePoint tenant app catalog.

3. Create a new team in Microsoft Teams (e.g. Team1). This will automatically create a related Team1 site collection in the SharePoint tenant

4. Add the SPFx App to Team1 site collection. The default app alert should display on each page.
   

5. Add a new general list (List1), a document library (Library1), and a modern page (Page1) to the Team1 site

6. Open Microsoft Teams and add three new SharePoint tabs to default General channel of Team1 (1st for List1, 2nd for Library1 and 3rd for Page1)
   

7. Observe that the alert is not displayed for List1 and Library1 tabs in MS Teams.

8. Alert is only displayed on Page1 tab

Expected behavior

SPFx ApplicationCustomizer scripts should be loaded in each list and library SharePoint tab in Teams.