I looked into these the other day as my canon inkjet is on its last legs, but it seems any brother laser printer with a comparable featureset now has its own subscription model, and I could be wrong but this is how it seems to work based on my research:
You automatically get a trial subscription with the toner you get in these printer models (not sure, I hope it’s opt-in)
If you don’t continue the subscription after the trial, the toner cartridges lock and there’s no way to continue using them, even if you renew your subscription later. You have to pay for new toner cartridges.