If you want to hide issues from Kanban board after closing them, you need to release them. The link Release can be seen on top of rightmost (Closed, Done) column.
Actually, the idea in Releasing a version (Kanban) is the fix version because by default Kanban boards have below JQL in Kanban board sub-filter setting in Kanban board configuratons
fixVersion in unreleasedVersions() OR fixVersion is EMPTY
If you release the closed issues, then they will not be either in unreleasedVersions() or their fix version would not be empty, which means they will not be seen in the boards.
I hope I was clear.
If this answer helped you, or you believe it is the right one please accept it so that other community users would benefit.
And for the clarification, please do not add other unrelated contents' links, I'll have a look though.
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