This was working with kde4 for me, but after upgrading to plasma, it only works for some programs. For example the kwallet chromium requests is auto-unlocked, but any plasma 5 widgets like "GMail feed" still request me to input my password. I have disabled closing the wallet after applications stop using it or after inactivity.

I have followed this guide to set it up, and the first approach did not work, but the one with editing the login manager files does, partially, as described above.

How do I get it to unlock kwallet5 (I guess?). I'm on arch linux x64.

pam_kwallet wasn't ported to KF5 (yet). I'll have to see about contacting the developer.

I see. Will it be possible to unlock both kde4 and kf5 wallets once and if it's ported to kf5? Or will my problem invert itself until all kde4 apps are replaced by kf5 ones?