Trevor Perrin and Moxie Marlinspike won the Levchin Prize at Real World Crypto for Signal's cryptography; the Levchin Prize referees are a who's who of academic cryptography, including Dan Boneh, Kenny Paterson, and Nigel Smart; other Levchin winners have included Hugo Krawczyk, Mihir Bellare, and Joan Daemon.

Any suggestion that Telegram's cryptography is somehow comparable owing to "half of them Ph.D's in math", or that Signal's extensively-reviewed cryptography is backdoored, is pretty clearly risible.

OTF, meanwhile, funded basically the whole of the privacy-preserving cryptography field, for years (they may still, for all I know); for many years, they were simply throwing money at privacy projects to hire 3rd party auditors, none of whom were at all affiliated with OTF (how I know this is that we participated). People who claim OTF is somehow a snakey USG backdooring enterprise are saying more about themselves than they are about any kind of sophisticated understanding of how crypto software is built.