Rated 4 out of 5 stars

to fix autofill:
either swith to the KDE5-Version of the Plugin OR
use the KDE5 Version of the method searchLogins inside KDEWalletStorage and compile the plugin yourself.

URL to KF5-Version of the method:
https://addons.mozilla.org/de/firefox/files/browse/521991/file/components/KDE5WalletStorage.js#L224

to fix sync:
- disable KDE wallet
- setup sync and use copy the credentials from the internal password manger
- enable KDE wallet
- paste the content to the key somesync@log.in,,Firefox Accounts credentials,chrome://FirefoxAccounts and the field password

the credentials should look like:
{"version":1,"accountData":{"kA":"somedata","kB":"somedata"}}

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