Hi!
There is absolutely no problem with Russian in Yealink. I provided you an Yealink official Russian support site.
Step 1. Flash firmware from this site (v.
X.60.XX).
Step 2. Reset phone to default.
Step 3. Check in the phone wen interface, that Russian is available. Also you will see Russian option in the LCD Screen menu (LCD Screen option switch to Russian LCD display only, but web interface remains in English).
Step 4. Add this in the general Yealink template
<option value="Russian">
<item name = "langwebUI">Russian</item>
<item name = "langlcdUI">Russian</item>
</option>
Step 5. Now you have to regenerate a provisioning files. Open Extensions one by one, set Russian and close.
Step 6. Select all the phones in the Phones Node and press Reprovisioning.
Step 7. Phone will reboot twice and wil be set to Russian.
Please, make this trial for us!