Adding overlay buttons with netplay_game_watch, netplay_player_chat, and netplay_fade_chat_toggle actions works on Android RA, images below

One can go to Settings > User Interface > On-Screen Display > On-Screen Overlay > Overlay Preset, to select the downloaded one

Netplay on Android can cause disconnects when bringing down the system "curtain menu", and switching apps

The extra buttons uses images of the built-in flat gamepad overlays, the buttons only work if a netplay connection is currently active

netplay_game_watch is used to swap controllers in netplay; pressing the button assigns you the lowest player number available if you haven't one, or "leave your controller" if you have one assigned, its icon is the rotating arrow

netplay_player_chat, brings the built-in keyboard menu and prompts for text to send on chat, its icon is a keyboard

And netplay_fade_chat_toggle, toggles between chat slowly fading out over some seconds, and it displaying the last 5 messages without transparency