[actionfromafar]

Are there for instance "cyrillic" fonts which (ab)use mappings to show as many letters as possible as latin letters, so for instance "трактор" would show as "traktor" but where letters which have no non-ambiguous latin representation would show as the original cyrillic letter?

( And persian ی would I guess show as y )

[tdeck]

There was a Cyrillic code page (remember code pages?) designed so that most letters would be at the same code point as corresponding Latin letters, just with the high bit set:

https://en.m.wikipedia.org/wiki/KOI8-R

[bonzini]

And with uppercase and lowercase exchanged!

There was such a font too, it was called Czar. I used it in Windows 95/98.

[Muromec]

Just learn Cyrillic. It’s easy and takes less time than figuring out font hacks

[vkethana]

probably doable with a chrome extension + search and replace