It is (still) not possible currently to insert a bookmark with Google Docs for Android (version 1.20.494.04.33). The only option to insert a bookmark is via the computer as stated on Docs Editor Help: Work with links, bookmarks, section breaks, or page breaks:
Add a bookmark
Bookmarks are not available on Android; you’ll have to use a computer.
On Android the communication between the web browser and the sms app bases on "Intents".
based on your description the problematic component in this set-up is the web browser.
Hence using a different app that can send Intents to other apps or using the adb shell can be helpful for testing out SMS links directly.
There a a lot of apps in Google ...
If I understand your question correctly, you want to: