Failure in migrating from J3 to J4

What I noticed after migrating JP Stella from Joomla 3.10.2 to Joomla 4.0.3, following JP Constructor and JP Standard.

The number of Japanese language files on the management screen is approximately 290 more than the English language files!

There is also a difference in the number of extensions, but just to be sure, if you check JP Constructor and JP Standard, there is a difference of about 300 to 400 files. I had no choice but to migrate all demo sites from J3 to J4 again.

So I tried various things and found out that if the J3 Japanese pack is not uninstalled before migrating to J4, it will remain in the J4 Japanese language like junk. Therefore, be sure to uninstall the J3 Japanese pack before migrating to J4, and if you migrate to J4, the number of Japanese language files will be a few fewer than the English language files.

And even if the extension is compatible with J4, you can uninstall the components and modules used in the trash by putting them in the trash. After migrating to J4, install the extensions you use and re-enable the components and modules you put in the trash.

Also, of course, there are components and modules that cannot be migrated, so it is necessary to configure them again or to configure them as new. The important thing is that if you keep the contents of your Joomla-operated site organized on a daily basis, the transition will be surprisingly painless.

By the way, if the extension is not compatible with J4, it will naturally not be possible to migrate.
I wasn't sure if I should explain it in more detail, but the handicraft content has been delayed quite a bit, so I'll summarize it briefly in text this time.

Well, I did a keyword search for "Joomla Japanese" for the first time in a while, but as usual, only the official and a few websites are useful. This is the reason why Joomla users will decrease...