i've updated/installed these files in
TL:Master/texmf-dist/tex4ht/ht-fonts. thanks.

alias/ec/ecxc.htf
alias/lh/lh-t2a/labi.htf
alias/lh/lh-t2a/lait.htf
alias/lh/lh-t2a/latc.htf
unicode/lh/lh-t2a/lacc.htf

First, I'd like to thank for the support given here:

https://tex.stackexchange.com/questions/392172/tex4ht-and-theorem-style-in-bold-face-and-small-caps

I've found the following issues:

The file lacc.htf contains a wrong line

'Е' '' 229

&#x0435 should used instead of &#x0415.

I don't know if the normal and the bold fonts use identical encoding but for me the following contents of lacc.htf worked well:

.larm
htfcss: lacc font-variant: small-caps;

Also, I found that support for the following fonts is missing:

labi.htf

.larm
htfcss: labi font-style: italic; font-weight: bold;

lait.htf

.larm
htfcss: lait font-style: italic; font-family: monospace;

latc.htf

.larm
htfcss: latc font-variant: small-caps; font-family: monospace;

laxc.htf

.larm
htfcss: laxc font-variant: small-caps; font-weight: bold;