There are two options. But only one I recommend when using Xposed.
So, here is the Xposed option.
Do not run the systemless Xposed module from Magisk.
Install the the Xposed manager and it's v89 package, then install the no device check Xposed module. Xposed will function just fine when making Magisk run in limited mode.
If not using Xposed, install the safety net fix module within the Magisk's repository.
The big reason is Google play server and Comcast Xfinity detects the TV box as a Mi box or Mi6 phone, with the universal Safetynet fix installed. Play server will make two devices tied to your account on the box. Eventually after 6 months the secondary box will be deleted.