I believe that tmobile was the ONLY carrier phine to get into the beta for the note 20. Otherwise only unlocked phones were allowed in. The beta has been filled though afaik
I've had T-Mobile before I bought my Note 20 5g from Samsung. I've participated in this year's beta and last years beta program. I actually do believe T-Mobile is the only carrier that is allowed to let their customers with network locked devices participate in beta tests on occasion.