“We’re aware of reports that access to Signal has been blocked in some countries,” Signal says. If you are affected by the blocks, the company recommends turning on its censorship circumvention feature. (NetBlocks reports that this feature lets Signal “remain usable” in Russia.)
Indeed… for example OTF (who is funded by US Congress) has provided funding for several large open source projects like Signal, Tor, F-Droid etc. and some have taken this to mean they might be compromised… but of course there’s no actual proof of that to my knowledge. And even in the linked article the author appears to use a bunch of half-truths and just straight up makes things up that don’t actually exist in the sources they say contain what he writes (example: OTF/Congress is not the CIA).
Personally I don’t have any suspicion or reason to believe they might be compromised, but if such proof ever did come around… I wouldn’t be surprised.