DreymaR, you know that I'm not using standard keyboard, this is why I did not provide the diagram, because it is made for Dactyl Manuform, which is having two extra keys at the bottom of each side. I use these keys to put extra Russian letters which resides in the right pinky area. Also, because I use Colemak DHm, that influenced the layout.
Here it is.

Я Ж Ф П В    Й Л У Ы Ю
А Р С Т Г    М Н Е И О Ъ
Ц Х З Д Б    Ч К , . Ё
    Щ Ш          Ь Э

Other changes, I'm trying to eliminate outer pinky column from using it for apostrophe, this is why Ь is moved and rare Ъ placed at its spot. "/" is not used in Russian typing and ? exists as shift-7, so I decided to put Ё there.

Other version (just for core 3x15 letters area) is based on vanilla Colemak, which I believe works good for Rulemak for the left half (frequency order is В Д Г Б). I may consider to use this version if I decide to move further to better optimized rather than intuitive Rulemak.

Я Ж Ф П Г    Й Л У Ы Ю
А Р С Т Д    К Н Е И О
Ц Х З В Б    Ч М , . /

Dry remaining of these, what I mentioned in my previous post, swapping of Ц and З, and moving K out of corner and putting Ч in that place.

Yes, putting point and comma to the same key and calling comma with shift is a shame of the Russian layout (BTW, Russian typewriter layout does not have that issue).
Regarding Ё, I as a native Russian speaker may not use it and be fine, there are mostly foreigners complaining about Ё substituted with E. While the meaning of a word may be completely different with E instead of Ё (все всё), it is understood in context. And sure in verbal speaking there is no such substitution happens. I'm really not sure why such practice appeared at first place. Lately I'm trying to use Ё while typing.
I do care about core Cyrillic only (I mean the letters used in Russian, I'm not sure what may be called the "core", may be Bulgarian which has less letters, but definitely not Ukrainian or Cyrillic used in non-slavic languages).

By way of comparison, here's the Bulmak currently in EPKL:

And the Rulemak currently in EPKL:

As a native I've enjoyed ckofy's layout, though в is in a bad position. Also х/ч is an interesting choice, because of their frequency I think current position is right. Since I'm Colemak-DH user, here's how I'll do it for my pseudo-wide mode:

Ф Ж Я П Б    Й Л У Ы Ь Ю Ш
А Р С Т Г    К Н Е И О
Ц Х З Д В    М Ч , . Э

Btw, what I mean by "pseudo-wide": when I tried wide mode, I really disliked the stretch I had to do with my index finger for central keys. Also I'm on ANSI keyboard, so I didn't have that one extra key, though it wouldn't help me anyway. So for keys that are B and N in qwerty, I made with Karabiner elements that left shift if pressed alone sends B and right shift N, and the Y and H I decided not to use at all, and to hide these missing characters on the 3rd layer. With English it worked perfectly: I got rid of backslash and semicolon (; and : are perfect match for , and .), but with Russian it became a little harder because it doesn't have much to get rid of. Well, having some keys on 3rd layer isn't actually that bad, also I'll build a better keyboard in the near future.

I do. I liked the idea of having just 2 layouts, Latin and Cyrillic, and to use them for all languages that I need, but when I tried it I didn't really like it and decided that having a specific layout for every language is better. Pressing "change input source" shortcut 3 times may be tiresome, so I decided to make a specific shortcut for every language (I have a lot of free space on my extend/hyper layer).
The thing is that I type in Ukrainian rarely, but when I do it's probably something big — like some university assignment, so I get tired by using 3rd layer too much. You see, щ is a pretty rare letter, also I placed it on a home row, so it's a nice enough position on the 3rd layer. But having Ukrainian i on 3rd layer didn't work for me because of how frequently it's used. Also I use 3rd layer for a lot of other things, it's hard to find good position for everything.

It's really similar to the emacs vs vim debate. These 2 are the best text editors for software engineers, because they have a lot of ways to edit the code, doing many things with just several keystrokes. But emacs uses shortcuts, like all normal programs do, and vim uses separated edit mode. So to undo in Emacs you do Ctrl-/, and in vim you just press "u" while being in edit mode. And vim way of editing is much better. You press esc once to get into edit mode and do what you need, instead of holding Ctrl and getting what is called "Emacs pinky". Because mostly it's not a single command you need to execute.
The same with using different languages. I better press shortcut once than press altgr 100 times.

Ah, that is an interesting consideration! However... might there be a way to get these consonants away without moving O? For instance, ш щ can reside on one key using the AltGr positions for щ – don't you think so? Maybe on W, I don't know. Any thoughts?