Draft language packs for Pale Moon 28 (on UXP) have been announced here:
https://forum.palemoon.org/viewtopic.php?p=144777#p144777
which takes us at:
https://github.com/JustOff/pale-moon-localization/releases/tag/28.0.0_RC1
As noted,
These are of course installable on @roytam1's New Moon 28 builds (PM28XP pre-release builds), but be warned that because Pale Moon 28 is still undergoing many GUI changes, they (Language Packs) are prone to break with any future release . After the installation, remember to modify the value of pref general.useragent.locale accordingly and restart the browser, in order for the pack to be used...
In the event of a future break
1. If the browser is able to start and AOM is accessible,, disable the language pack (in about:addons) and restart, to go back to the default (en-US) localisation.
2. If the browser GUI is totally broken and won't start, then start in safe mode and permanently disable/remove the culprit LP. Or locate in Windows Explorer your NM28 profile and manually delete file "./extensions/langpack-[x]@palemoon.org.xpi", where [x] is the code for your language (e.g. en-GB), then start the browser normally...
You should keep an eye on the linked GitHub page for newer, fixed, releases...
@kitaro1 : Polish LP for NM28