The claim I’ve heard most is that Kalashnikov based the design of the AK-47 on the STG 44, but I’ve read a comment on this site (as far as I can remember) from a user whose username I can’t remember who said the opposite: That Kalashnikov did not base the design of the AK-47 on the STG 44
https://smallarmsreview.com/the-assult-rifle-comparison-of-the-soviet-ak47-to-the-german-stg44/