Saw your post in GoldenTouch thread. Decided to just go ahead and make it, using the languages you displayed.
Widget 1 - Current Language - Displays current language as a flag, on press opens languages group. Changed it so that the icons are emoji flags
https://share.folivora.ai/sharedPreset/179507fd-325a-462d-a9a1-5d65bae6c43d
Language Groups - Shows different languages/input sources, press each one to switch to that input. Also shows current language on the left. Press to close the group.
https://share.folivora.ai/sharedPreset/5f5d3794-59c9-42a8-9fb9-5d45605f6b1d
Let me know if it doesn't work for you.
If you want it under a modifier button, like opt, make sure you set the languages groupt to the same modifier.