Honestly i believe there is no point in speculating whether there are backdoors installed in popular privacy and encryption apps; for all we know, the powers that are may already have a digital fortress'esque quantum computer decrypting everything from your signal messages to onion sites in a matter of seconds.

I think(my personal headcanon) that there probably was a Manhattan project like top secret research project that has yielded some very fruitful results, now i guess we have to just wait for some whistleblower or a disgruntled employee to feed it a file that blows it up.