This version of com_localise is Joomla 4.0 ready.
Uninstall all former versions on a local instance of J4 and install this one.
Using en-GB as admin language can help to create the setup.
You may have to modify some php.ini parameters to cope with large ini files.
Examples:
max_input_vars = 10000
memory_limit = 1024M
post_max_size = 256M
upload_max_filesize = 254M
Then make sure to load the Languages view first and then Options to set your parameters.
If you enable en-GB reference language and development (screenshot above, advised), save, open the Translations view, select client and the target language, it will take some time to get the display. This is normal as it fetches through github the last 4.0-dev in files and then compare them to your language.
If your original installed language pack has been done on crowdin, the default plural forms (when they are simple, as en-GB) are not the en-GB default one... (Grrr)
This means that com_localise will display the strings concerned in the Not in Reference section and the en-GB plural strings show as untranslated.
If you intend to go on translating on crowdin and just use com_localise to check errors, etc., then keep the crowdin plural forms.
If you drop crowdin (except for the installation part), you can safely delete the crowdin plurals (ONE, OTHER) and translate as usual the en-GB variant in the normal section.
Settings as Complete, Copyrights, etc. should be similar to com_localise for J3.
Package making is simplified.
Please post any issue in this repo.