For the record,
here is the Jastrow "Dictionary of the Targumim, the Talmud Babli and Yerushalmi, and the Midrashic Literature" in he-en dict form, suitable for KOReader (
https://kindleseforim.paritcher.com/) (
https://en.wikipedia.org/wiki/Marcus_Jastrow). In KOReader's dictionary viewer I see serious bidi issues, as I saw with the Vicons above, so I think they are an intrinsic flaw of KR. Compare for example the attached screenshot with the original dictionary page at
https://www.tyndalearchive.com/TABS/Jastrow/
ETA: known KOReader issue:
https://github.com/koreader/koreader/issues/9320