Finally checked out EchoPark Automotive Dallas (Grand Prairie, TX) after seeing their lot on my commute for months. They keep around 117 vehicles, mostly family SUVs and sedans. They were totally fine with my mechanic doing a once-over, which honestly settles half the trust question.
Lot address: 2615 I-20 Frontage Rd, Grand Prairie, TX 75052. Visitor parking: Customer lot on I-20 frontage. Website: https://www.echopark.com. Board status: verified / trusted dealer.
Paper side: licensed with the state (looked it up), about 81% of stock has title in hand per the office, and they offer a 6-month powertrain warranty on newer units.
Overall: mixed feelings. Cars looked right but I got two different answers on a title question, and that's my personal tripwire. If you go, get the title status in writing before any deposit.