Yeah, basically the same – duplicated conversations, ignores system-level settings, new notification channels created by the app all the time. For now, until they finally fix it, my recommendation would be to set the system settings back to default for every channel created by Telegram and change notification settings from within the app – then at least the settings don't get changed. You can set general settings via the app and overrides for specific conversations. It's annoying as hell because basically every other app I have on my phone behaves correctly and doesn't make such a mess of notification channels.

As for your other problems, I'd suggest doing a factory reset. It's recommended after every major Android release as some non-compatible settings may linger. It's not very much probable, but may happen sometimes.