I am quite frustrated by the same behavior on my Samsung Android phone. After selecting a small amount of text and lifting off my finger the selection handles do not appear. However, pressing that same text afterward causes the handles to appear again.
In my case however, an even bigger problem is that when dragging down a page with my finger to select large amounts of text the selection process freezes and the handles disappear after selecting perhaps 200 - 300 characters. This is repeatable.
The other problem is the difficult, jittery, process of dragging the selection handles, especially when selecting HTML links. This makes it difficult to select larger sections of text precisely.
Overall this clunky selection process on Android is one reason that keeps me from fully embracing Obsidian as my go-to writing app.
Not working consistently for me either on Android 12. Selecting text is tedious on mobile anyway so I wish there were a way to just copy the whole note with a command or dropdown menu button. Copying as HTML would be even sweeter (there are plugins that do this but they don’t work well with mobile).