T-Mobile Home Internet with LB 1120 ?

Not much doubts the T-Mobile Home Internet SIM should not work.

Supported T-Mobile bands in the US
5G Bands: n25, n41, n66, n71
4G LTE Bands: B2, B4, B5, B12, B41, B46, B66, B71

I'd be more concerned about the limited bandwidth possible on the pure 4G-network vs. the 5G offering. A staring point for evaluation could be https://www.t-mobile.com/responsibility/consumer-info/policies/internet-service which depends on the band and the contract (like Wireless Home Internet vs. Wireless Small Business Internet).

Wireless Internet 
5G Network (Wireless Business Internet):

Download Speed: Typically between 77 – 292 Mbps
Upload Speed: Typically between 18 – 31 Mbps
Latency: Typically between 19 – 37 ms

5G Network (Wireless Home Internet, Wireless Small Business Internet):

Download Speeds: Typically between 72 – 245 Mbps
Upload Speeds: Typically between 15 – 31 Mbps
Latency: Typically between 19 – 37 ms

4G LTE Network (Wireless Business Internet):

Download Speed: Typically between 37 – 119 Mbps
Upload Speed: Typically between 7 – 25 Mbps
Latency: Typically between 24 – 40 ms

4G LTE Network (Wireless Home Internet, Wireless Small Business Internet):

Download Speeds: Typically between 30 – 110 Mbps
Upload Speeds: Typically between 6 – 23 Mbps
Latency: Typically between 24 – 40 ms

The possible 4G LTE numbers fit well into the capability of the LB1120, needless to say this device does not support 5G.