No changelog entry since bug was introduced in test release

I don't know if this is the right approach. The fact that useDraft returns draftState of the previous chat after you switch to a chat to which you cannot send, seems pretty wrong.

In a readonly chat there should be no calls to setDraft or load draft at all. So if you prefer a minimal approach we could add the !canSend condition only to the shortcut in https://github.com/deltachat/deltachat-desktop/pull/4394/files#diff-ca83809f74f6819ef5c7d61676ac6c9abd27cb5becc46cb08bc9c43bc87c0f61R596

btw: it seems clearDraft is nowhere used outside of useDraft, so no need to return it.

In a readonly chat there should be no calls to setDraft or load draft at all

There was this MR #4342 which suggested making the draft editable even when !canSend.
But if we decide to make the draft non-editable when !canSend, we should probably make useDraft return a value where these functions (updateDraftText, removeQuote) can be null or something like that, instead of silently doing nothing.

But maybe I'm being too pedantic.

So if you prefer a minimal approach we could add the !canSend condition only to the shortcut

In this particular case yes, I'd prefer to be more conservative, but I won't insist.

Returning null would mean to add non null checks in many places. I also don't like that loadDraft is called even in !canSend chats. Maybe it makes sense to add another clearDraft() call in loadDraft before returning.

instead of silently doing nothing

I would say: these functions should never be called, but if called they should not add a draft to a readOnly chat

Returning null would mean to add non null checks in many places.

Well yes, that's the point. You don't want to call a function that you expect to do something but that actually does nothing.

Maybe it makes sense to add another clearDraft() call in loadDraft before returning.

Yes, that's better than keeping the previous state of the draft. And clearDraft() doesn't clear it in core, so it's alright.