I used to use Keepassx on Kubuntu 20.04 to manage my passwords but recently I have been using Bitwarden. It is a lot simpler to sync between devices and I like that it is almost purely focused on secure password management. It also meant that I could stop using the password managers built into web browsers and have a one stop shop across all my devices.
Currently there are versions for,
There are also versions for the command line and on the web. It's a pretty complete list. Additionally it is open source and you can host your own Bitwarden server if you want to go the additional step but the basic account is free and includes all the features that most people need.
To install Bitwarden on Kubuntu 20.04 go to their downloads page and click on the Linux link. This will download an appimage file (you might also be interested in the Appimagelauncher if you want to manage your appimages). Right click on the image and choose Properties, then the Permissions tab and check Is Executable. After that you can double click on the image to run it and log in. Of course, you can just log in through their web portal as well which can be found at https://vault.bitwarden.com
Give it a go, it won't cost you anything and solving the password problem might just save you someday.