Currently TMT250 uses the same FW as FMB series devices.
TMT250 support was integrated into common FMB FW starting FW version 03.19.00.Rev.00.
Latest integration is [03.21.01.Rev.01] as listed in TMT250 errata document.
So unless something changes, FW version 03.21.01.Rev.01 - can be used for TMT250 and any other FMB series device (except FMB64).
Regards