As far as I gather it is considered socially trustworthy (they will not add spyware to the app like some doubt of Facebook's WhatsApp) but not as technically trustworthy (early on people reported that they received messages of groups they never joined and there is a lot of homebrewd crypto).

personally I care more about the fact that it is an actual possible competitor to big tech in terms if userbase and functionality than it being less secure than signal

I feel like IM is a pick-your-poison kind of deal. Signal is technically superior, but it's UX is laughably bad. Facebook, Microsoft, Google and Apple are cartoonishly evil corporations. Telegram is a bit rough in places, but has to me been the least offensive of the bunch.