You can use https://plex.tv/web/ to set your language settings and then keep using your local Plex Web. As long as you don’t open the language settings there and click on Save it will use the ones you specified using plex.tv/web
Plex Web use to auto-update itself then people complained they didn’t want that so it was stopped. It was also causing issues as some newer Web versions require a certain PMS version, so if you update Web without updating PMS you get stuck.
If you ever want to run the latest version of web, you can always run the version from Plex.tv.