This has been discussed for quite some time, but apparently RoboSats is getting more serious about moving away from Telegram. They have a SimpleX chat available. It didn't seem that active when I looked a month or so ago, but is now more active.
AND they're also setting up a Nostr based implementation on https://www.0xchat.com/. I'm looking forward to trying that - I haven't done anything Nostr-related in more than a year, but I know I should be.
Here's the details from the RoboSats telegram group:
As you already know, this group has been obsolete for months due to Telegram's policies. The constant attacks on privacy, security, and freedom in communications led us to seek alternatives months ago.
We found the greatest security and privacy possible in SimpleX and created a group that currently has over 1,000 active users and is one of the largest channels on the platform: https://simplex.chat/contact#/?v=2-7&smp=smp%3A%2F%2Fu2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU%3D%40smp4.simplex.im%2FuAn-yqUc9UOOQSUESM9jPOdkQt7mqamr%23%2F%3Fv%3D1-3%26dh%3DMCowBQYDK2VuAyEAZaHuArdHZ1UENbpo5tWt2QtjoiFG2gPsb5_3J5oXIQg%253D%26srv%3Do5vmywmrnaxalvz6wi3zicyftgio6psuvyniis6gco6bp6ekl4cqj4id.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%22UPU1-wZKatLYYoyeX7HGyg%3D%3D%22%7D
We're also on Matrix: https://matrix.to/#/#robosats:matrix.org.
Today, we're launching our 0xchat (https://www.0xchat.com/#/) group, where you'll find a pleasant interface and a secure protocol on Nostr >nostr:naddr1qpqrjv34vgckzcfjxp3kgvtzxcuxgepevycrzvesv5en2wps8pjrvd3hxuexvefs8qexxe3nvcun2v3ex3jxgdfhx56kxdm9vyck2ep48yq3wamnwvaz7tm8wfhh2urn9cc8scmgv96zucm0d5pqqqcyqqqfskq06gxuf.
The final closure of Telegram is getting closer, but we'll continue to meet in the Atlantis (https://amberandchaos.net/?page_id=73).