I just experimented with flashing the T-Mobile firmware on my Canadian SM-N986W, and I wanted to share my takeaways:
1. Flash succeeded with Prince Comsy.
2. A greyed out eSIM (and its IMEI) appeared right away in Settings, About Phone.
3. Settings, About Phone, Status, SIM revealed no MEID for the eSIM.
4. Settings, Connections was missing a SIM Card Manager.
#3 is necessary for activating an eSIM
#4 is necessary for managing a dual SIM phone.
5. Last but not least, T-Mobile doesn't use band N66 for 5G, and I don't know if not having a t-mobile SIM led to errors 1-4, but even if it did, getting 5G to work on Bell was not going to be straightforward.
After this adventure, I flashed my 986W back to the Canadian firmware and started praying that one day it will be updated to support DSDS