I suggest using Riot, preferrably self-hosted.
To add to that I can use Signal just fine with Google Voice. So if both Telegram and Signal require a Google voice number, might as well go with Signal.
It makes no sense to create a "secure" chat app, and then to force your users to use cellphones, which is the most unsafe technology I can imagine... Why this cellphone fetish?
- you are tracked everywhere - you don't control the software for real - you have almost no control on connectivity - it's super difficult to kill a process
etc.
Also there are not good free software mobile operating systems, sure there is LineageOS and other ROMs that still require some proprietary parts, mainly the firmware of the device and binary blobs in the kernel, for one person concerned about privacy that is a problem, because proprietary software means backdoors, and it's useless to use a fantastic free software secure communication app if we can't trust the OS where we run it.
Apple's reality distortion field in full effect...
Neither Android nor iPhone can be considered secure.
How did you sign in without a phone number? It's not possible on https://web.telegram.org/#/login.