Title is a bit misleading. Those channels are not blocked on Android in general, but only on the play store version of telegram. Download from F-Droid instead and that's that.
This is why sideloading is always an essential function for any devices in general. How come I buy stuff and do whatever the fuck I want with it?
Don't get me wrong, although I think it's quite clear, Hamas, obviously bad. Very much understandable of Google's decision. But a company(apple) deciding what is and what is not acceptable to be installed on my device? It's just uncanny how acceptable it is. That's like buying a car that can't go into certain places because uSeR sAfEtY. Even if I probably would never go there, why on Earth would you want that?
They shouldn't submit to arbitrary censorship, even if I also disagree with Hamas, Google could do it to anyone they disagree with. Telegram should move to (or at least also be on, with an uncensored version) F-Droid.
This is just another parameter that will now be built into future chat software; no high level control over channels or groups by any central authority. The Internet will route around all obstacles.