Thanks for @Guido07111975, Dutch translations files are now available to install from the API 
These should start to show as Translation file transit data is updated periodically by ClassicPress installs.
Great!
I have now manually added the 4 Dutch (nl) .po files and was able to select Dutch (Nederlands) in my dashboard. Will remove the files later this week and see whether they are auto-installed again or not.
Somewhere on the www I saw that there are still more v1 installs than v2 installs? Is there a need for completing that translation as well?
Guido
I wouldn’t do the translation for v1. We really want users on v2.
Understood, will not touch the v1 ones 
Hi @MattyRob
This week I’m updating strings of the Dutch translation, but I don’t get notifications in my dashboard about updated translation files.
Is this part of the limitation you’ve mentioned in a previous reply?
Yes, that is the limitation, updates to language packs need building and adding a zip files on the API site, and even then the current core code does not easily allow in-version translation file updates.
What’s the best approach for now, how do other users get the updated translation? Will the files be (manually) added by the release team to each updated version of CP?
Guido
My idea is to update translation packages prior to each release if there have been updates / changes and I’m notified at the time. Last release we had a string freeze to allow this to happen.
If you want to access your own updates quicker try the following, you will need WP-CLI locally:
1/ Update the 4 *.po files as needed
2/ In the same folder as thos files run this command: wp i18n make-mo nl_NL - this should create 4 *.mo files.
3/ On your sites server, using FTP software navigate to wp-content/languages, and upload the 4 new *.mo files.
4/ The updated strings should now be translated.
Agree.
Between you adding Dutch support and today I’ve updated quite a few strings (almost finished with double-checking).
Are you able/willing to create a new langage pack later today, so users that are switching to Dutch are getting the most recent translations?
Guido
Let me know when it’s completed and I can update the zip for new users / installers as my time allows.
Done for now.
Are you updating the .pot files at Crowdin before releasing each CP update? So translators can update the translations before each CP release.
Guido
Yes, the POT files get updated before releases.
@Guido07111975 Apologies for the delay, but your updated Dutch translation files should not be available via the API.
Thanks!
Meanwhile I did update a few again, but they can be added in a future release.
I did notice that a couple of strings at page Site Health are not translatable.
They are located in file wp-admin/js/site-health.min.js.
This file is currently not present at Github, but I notice you’ve worked on the wp-admin/js/site-health.js file? Did you fix this as well?
I don’t recall doing any work on that file specific to strings, which ones can’t be translated?
All strings in that file, such as %s recommended improvements.
No reference to that file in Crowdin / po file either. But there are references to the non-minimised file wp-admin/js/site-health.js.
And, as mentioned before, the minimised wp-admin/js/site-health.min.js file is removed from the develop branch in Github.
Guido
Hmm, interesting - it seems that minified JavaScript files are excluded from POT file creation, but this mirror upstream. This will need more investigation to understand how this is all supposed to work.
You’re right, I don’t find any references to a .min.js file in the po files.
Are you gonna pick this up or should I report this at Github?
And why is the wp-admin/js/site-health.min.js currently not present in the develop branche?
This becomes off-topic btw…
Guido
There are no minified files on develop as these are all built only on release. Minified files are not used in the development code, debugging is easier that way.