Is TM Home Internet going to work for me?

I have been using a Ring alarm system and Ring doorbells with T-Mobile Home Internet  (Nokia gateway) since August 2021, and it works perfectly (I'll get to intermittent service in a moment). My Ring setup was installed when I had AT&T DSL service.  I have an Orbi mesh system that connected to the AT&T gateway via ethernet cable, and all the Ring devices were connected to the Orbi mesh network. When I switched to TMHI, I just plugged the Orbi ethernet cable into the Nokia gateway. Everything worked properly without my having to make any changes other than restarting the Orbi after connecting it to the Nokia..

About service interruptions--my Ring alarm system (the first generation) has a cellular failover system.  I pay to have my alarm system monitored, so that I get notified if the alarm is triggered, and so it can notify police, etc. If my TMHI gateway loses the internet connection, the Ring alarm switches over to cellular service, so my alarm system is still connected to the internet. I get an email letting me know it's switched over to cellular.  TMHI usually reconnects on its own, but it might take 15-30 minutes. Then Ring switches back from cellular to TMHI, and I get another email letting me know that.

If I want the TMHI internet connection restored more quickly than that, I can call T-Mobile Customer Service at 1-844-275-9310 and ask them to remotely reboot my gateway, and they will do so.  I've done that a few times while traveling, more as a test than as a lack of faith in the cellular backup.

A little more about my setup: I use the Orbi router in router mode, even though that adds an extra layer of NAT. I enabled IPV6 passthrough on the Orbi. I eventually added an ethernet switch that I connected to the Nokia gateway via its other LAN port. I plugged the Ring alarm base and my entertainment devices (TV, Receiver, Roku, Apple TV, etc.) into the switch.  My Orbi router still has some other home automation devices using it, including a smart thermostat for our HVAC system, as well as our tablets, phones, and laptops. I don't use the Nokia gateway's built-in wifi system, as that seems to cause some heat issues, but I've done speed tests via the Orbi and when connected to the TMHI wifi, and speeds are the same, so I'm not losing any speed by going through the Orbi.  All together, I have 14 devices using the Orbi, and 10 devices connected into the ethernet switch, though fewer than half of the devices are typically being used at the same time.

Good luck with your set up.  I hope you have as good an experience as I have.