This should rather be attributed to the "Bug" section, but not the point.

I finished the mod to the end, corrected a lot of spelling/syntax errors of the previous translator, and made some translations more understandable and correct. I would be grateful if you update the localization in the mod.

I would also like to report a small localization error. In the key "item.travelersbackpack.tier_upgrade_tooltip" the string is formatted: the %s variable is inserted for the improvement level, that is, the improvement level is a hardcored string and cannot be translated.

ru_ru.json

I've uploaded updated russian localization that was submitted while ago by translator, please check if something needs correction if you can and provide changes to this file, it has all necessary translation keys for me to use for both Forge & Fabric

Here's the latest russian translation file:
https://github.com/Tiviacz1337/Travelers-Backpack/blob/1.20.1/src/main/resources/assets/travelersbackpack/lang/ru_ru.json