I installed Flatpak on the community version of Sailfish OS 3.4.0.24 then the Flatpak version of Telegram. It looks just like my desktop version of Telegram. The way I understand it is that Flatpak allows desktop versions of apps to be run as mobile apps on Sailfish OS. There were some problems at first with the Flatpak Telegram when I ran it. The problems seem to have mostly smoothed out. There seems to be a feature or two that have an icon that won’t work when pressed (like cannot send a picture or video yet, but can receive a picture). They will probably get implemented in the future, but it does look like a full real version of Telegram. I was making a voice call one day and the only sound output was on speaker phone. Is there anyway to turn speaker phone off with this version of Telegram? I can try earbuds, too, but was curious about some feature I had missed.
Don’t think ther is a way to do that from within Flatpak apps. I could be wrong though.
As a work around, you could use the application “Audio Output Chooser” from OpenRepos and choose Output to earpiece in the app when making a telegram call. That should route the audio to the earpiece. I haven’t tried this myself, but I think this should work.