apparently Proton has its source-code open (https://proton.me/blog/security-audit), regards Signal and the other search engine i don't know... i bet none of them are the panacea on privacy but it's also quite naive to counter the author rant placing Google, Meta and whatever are at the same ethical ballpark of the former companies when they were involved in a bunch of scandals over their history and are making A BUNCH of money on their evasive telemetry (often shaping culture, see what Youtube turned; click-bait titles, prolix dialogue because the algorithm of [more time watched = more revenue] and even questionable thing like "album reactions" or just silly stuff that feels an offense to the enviroment like filling a swimming-pool with slime or some absurd shit on Youtube Kids)
edit: i could also go on what Instagram turned out to be...