I installed KOReader following these instructions: https://github.com/koreader/koreader/wiki/Installation-on-Ko...

Wallabag plugin is built into KOReader. Launch KOReader by clicking the icon it puts in your Kobo library, then in the menus you will find Wallabag config. I added a "Wallabag Articles" folder for it to sync to.

Note if you use a password manager, my password had a double quote which I believe messed with the .lua config password string, so I was getting connection errors.

It took 80-90 mins to download 1200 unread articles to my Kobo. I haven't played with the auto sync function yet, so far I just manual sync before/after a reading session.

I've really got to be brave and try KOReader one of these days. I used Pocket because it was the one service supported on my Kobo. I don't want to replace the hardware, but I am mildly annoyed by the locked down and slow software.