Following are some bugs and issues when using Telegram app on foldable phones in unfolded mode (inner screen). (Note that the app works well on the outer screen.) (My phone is a Galaxy Z Fold 5.)
Video playback interrupts when rotating the phone, and it jumps to the chats menu.
Pressing back while in a chat redirected from another chat takes you to the chats menu instead of the previous chat.
The app fails to optimize itself when switching from the outer screen to the inner screen when unfolding the phone. It jumps out of the chat, preventing you from continuing your conversation from the outer screen.
Steps to reproduce
1.1. Unfold the phone (using the inner screen).
1.2. Play a video from a Telegram chat and switch it to full screen.
1.3. Rotate the phone.
1.4. The video is interrupted, and the app jumps to the end of the chat from which the video was played.
2.1. Unfold the device.
2.2. Open a chat or bot that redirects you to another chat or group.
2.3. Open the new group or chat by following the link from that bot or chat.
2.4. Press the back button.
2.5. You will jump to the chats menu instead of the chat screen you were previously on.
3.1. Fold the phone.
3.2. Open a chat and start typing something.
3.3. Unfold the phone.
3.4. The app will send you to the chats menu instead of the chat screen you were previously on.
Device info
Telegram Android 11.9.2 (59012), Samsung Galaxy Z Fold5, 14 (34)
The app does not optimize itself with foldable devices. sometimes it shows the chat list on the left side of the opened chat, but sometimes it hides and maximizes the opened chat, but buttons like forwarding or back button doesn't work.