I was wrong and I'm sorry about it. Turned out, I disabled one setting in my Google Chrome password manager, which apparently also disabled passkey creation functionality.
For my excuse I should note, that this passkey support is relatively recent (end of 2024) and error message was really unhelpful to understand the issue. I was trying to use passkeys on my Linux computer like every few months since they started to appear on various websites and was frustrated by lack of support in Linux.
Thanks for pushing me into right direction, so at least I can now use them.
https://issues.chromium.org/issues/417941069 more here.
For my excuse I should note, that this passkey support is relatively recent (end of 2024) and error message was really unhelpful to understand the issue. I was trying to use passkeys on my Linux computer like every few months since they started to appear on various websites and was frustrated by lack of support in Linux.
Thanks for pushing me into right direction, so at least I can now use them.