Hi everyone, thank u very much for your help.
I tried reinstalling Telegram and testing both the App Store version and the .dmg one but Kaspersky was still blocking my uploads to Telegram.
Fortunately, I found something in the Kaspersky settings panel that made the trick.
I just unchecked the "Safe Browsing" option and everything went back to normal.
I'm wondering if there is any way to add an exception to Telegram to keep Safe Browsing active. Thx 🥳