I think Trezor is using Closed source Elemnt Chip on the safe 3 and safe 5 models its not open source
We are talking about open source
firmware in hardware wallets, that is making a big difference, and ledger is keeping that closed source.
Secure elements in Trezor 3 safe is Infineon OPTIGA Trust M, they released the code on github and they reveal any bugs, unlike ST black boxes chips used in ledger devices.