Dates on the files on Harem Hotel v0.18.1 Patch Notes are old, from 2018 and 2021.
There is Patch 0.17+ -> 0.18.1 (Requires 0.17+), that seems to apply to patching 0.18 to 0.18.1, but the patch note says nothing about how to apply the patch. I play on Linux, is the patch only for Windows?
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OK, I downloaded the patch file and in the zip there is file READ_ME.txt that tells how to install the patch. I think that works also on Linux.