Fringer is testing their EF-FX Smart Adapter with firmware 2.40 on the Fujifilm X-T3 and it seems to be working quite well. This demo is in pretty low light and the focus accuracy and speed of the of the Sigma 50-100mm/1.8 through the EF-FX Smart Adapter is very good.
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Fujifilm X-T3: B&H Photo / Amazon / Adorama
Fujifilm X-T3 + 18-55mm: B&H Photo / Amazon / Adorama