> Afaik only rev. 2B5 is capable to use more than 1GB

That's what I thought, too, until June 2019 when I read sailor's report about Prober's (who himself reported it as long ago as 2015) 2B1 board.

> Rev. 2B1 I've never seen and it's new for me,
> that this rev. works with more than 1GB too......

I've never knowingly "seen" one either, yet I see no reason to doubt the reports of it working with 2 GiB RAM.