In the US, my accountant always (and as I understand it, the rules have gotten stricter) recommended against taking a home office deduction unless you really had dedicated space for equipment etc. The way more typical "office space you often use for doing work" was long seen as a red flag for a deduction and, in the typical case, as you say, truly dedicated space is rare absent a large place and/or specialized needs.

I could make a room a dedicated day-job office but it would cost me way more to do so than I would ever get as a deduction and it would almost certainly be inferior to the mixed-use setup I use.