From what I’m seeing here, you may have to move – possibly temporarily – to another Linux distribution.
For example:
openSUSE Leap 15.5 – do not dream about Tumbleweed – KDE Plasma Version 6 is currently being being built and suffering the effects of “openQA” and, as soon as the SUSE and openSUSE folks get the QA issues sorted out, it’ll appear in the Tumbleweed rolling releases …
Kbuntu.
Arch Linux – Plasma 5 is tagged as “Extra” – Plasma 6 is tagged as “Extra-Testing”.