Of course, nobody is going to have evidence here, if there was any the cover would be lifted. But one can guess chances here:
Proton: "Unlikely"... but there is a but. They never cater for the ultimate privacy and they make typical blunders of a company wanted to growth really fast. Now, that they want to be a behemoth in Privacy makes it more vulnerable to requests from law enforcement. Also, law enforcement and intelligence agencies have it easier to penetrate within Proton massive headcount growth.
Tuta: "Very Unlikely". The people behind started very young and had a sustainable growth. The people are very visible (unlike Crypto AG) so least likely to be working for an "agency".
Mullvad: "Very Unlikely". I think their story is similar to Tuta (haven´t followed it that much though).
GrapheneOS: "Very Unlikely". But in the last year I have raised some minor concerns, but I haven change my rating yet....
/e/: "Very Unlikely". I know the dude behind for 2 decades, he wouldn´t. However, /e/ never claimed full privacy and from the beginning says he would comply 100% with "lawful" requests, but it is not a honeypot, not that would make much difference to an intelligence agency if they wanted it.
Signal: "Potentially"... yes, yes... audited, solid privacy code... but still does not make sense to me many aspects; financially solvent from day one, the extreme unquestioned massive and vast support from launching till today... if i have to bet in all of these providers, this platform would have been my take as potential compromised one. I still use it to communicate with family since I trust better than WhatsApp, but I would not use it for critical journalistic info.