> The messages are mine, not theirs, and yet they refuse to allow me to handle them how I deem fit.
"They refuse to allow me" meaning "they don't add the features I want for free to the app they provide for free, so I complain".
The messages are yours, of course. But don't forget that you use their work for free. If you're not happy, go use the free work of someone else, I guess?
They are somewhat correct though, Signal has written code explicitly to prevent iOS users from including Signal data in Apple’s encrypted local and/or cloud backups.
Allowing encrypted backups was free for Signal, but they spent time and money to prevent it for iOS users.
Part of the code the wrote to prevent backups in question:
Lot's of people have requested justification in related Github issues there, but Signal has not given a clear answer. If there was a security problem with the encryption process I believe a CVE or similar would have been in order because it would affect millions of users.
Their first cut at "working on it" is to require that we pay Signal to store our backups for us (45 days of media and 100MiB total is not a useful free tier; I have more than 1 GiB of messages/media spanning years), when that's an entirely unnecessary restriction.
I don't know what you do for a living but it's very common when writing and releasing software to do it in phases. Earlier phases have a restricted feature set and feedback from the field/customers/users experiencing earlier phases informs choices in later phases.
Unless you have direct insights into their dev process, your claim that the restriction be "entitely unnecessary" seems overly strong.
The messages are mine, not theirs, and yet they refuse to allow me to handle them how I deem fit.