A prime one is that the entity that you (have no choice but to) trust today will eventually turn against you at some point down the road.

How does that change with federation, you always trust someone. Why should I trust the shady person running software on their basement, even if you self host, you are trusting the developers not to ship bad or poorly written code.

Federation is different in that:

• you can chose amongst a very diverse pool of providers, including local ones that you actually have a chance to meet in person, those with shared ideals that enable long-lasting/mutually-beneficial relationships, some operating truly in the open and enabling a just and provable retribution for the offered service (i.e. "you are not the product"), etc

• you can be your own provider, and with "turnkey" self-hosting options like https://snikket.org/ , it's never been easier to do it safely at small/medium scale, and cheaply (e.g. for a family/neighbourhood/association on a shared instance/RPi/…)

• choosing a provider never cuts you off from the rest of the network: you are not tied to anyone, and you can migrate with no drama nor loss of contacts/histories/data like is the case when the captive networks "flavour of the year" inevitably shut down.

using a 3rd party client is against Signal’s ToS

As far as it being against signals tos, molly exists and had not received any problems from the signal foundation to my knowledge, discord has the same clause and they don’t seem to give a rats ass.

You must be new on the internet to believe that this is a sustainable state of affairs. Google was letting you use GApps for free until it didn't. Reddit used to be mostly usable and ads/clutter-free until it wasn't. Recently Unity pulled a weird one against their users and customers for a quick buck. Examples are plenty, and more recently people have referred to this as "enshittification" or "the tyranny of the marginal user". Such monopolistic networks are particularly prone to that phenomenon, by design. Personally I don't want to live under the constant threat of a single entity potentially changing its mind/ToS, and I certainly don't want to drag my family, friends and peers into the gamble.

pushing controversial features like crypto payments

The crypto stuff wasn’t great but you know what’s cool? You don’t have to use it. Simple as that. You don’t have to engage with it and you and I both know that. It’s buried in settings and you have to find it yourself.

fair but you missed the point: Signal already controls and enforce this aspect of your user experience, which only benefits themselves, in spite of the significant backlash. Sure you can feign blindness, but what's next and what recourse will you have ?

Signal is an entity that’s incorporated in a jurisdiction and might be compelled by law or to degrade its encryption to comply with the local regulator.

I’ve always used integrity as a metric as to how trustworthy a service is, and in terms of signals e2ee, they’ve never lied about it, it’s been proven in court multiple times not having any data on their users, no government can compel anyone or any company for things they don’t have.

Integrity has nothing to do with that, Signal can absolutely be forced by law to suspend its service in some countries (e.g. to implement sanctions) and whole regions can disappear from the network overnight. In terms of resiliency, that's pretty much how email (federated) just works from anywhere, but things like WhatsApp are blocked in e.g. China or allowed to work without E2EE (e.g. in some Gulf countries).

You can’t really confirm what any software can or cannot do

Sure, but you missed my point, in case of sealed senders and contacts discovery, we are not talking about zero-knowledge/E2EE but about Signal basically saying "trust us, bro, we ain't looking at it" which can't be proven one way or the other.

If everything is encrypted, what could Amazon tap? You do realize sealed sender and PFS take away any trust from the server correct?

I'm not sure that you understand what's really going on. All your messages are routed through Signal. You can absolutely infer who's talking to whom with enough frames by just matching packets popping out of X and being received by Y. Encryption plays no role in that because this takes place at a lower level. At least some protocols like XMPP let you host services entirely on Tor or to even skip the central server.