Honestly, i hope you won't move away from Ren'Py, Harem Hotel right now could be play on weak PCs (I have a good PC but most of the time, I play Harem Hotel and other 18+ Ren'Py games privately in my room with my old laptop using Intel HD Graphics, surely my laptop can't handle UE5 games).It's hard to say, I don't know what my options will look like in the future, but my goal is to move to unreal engine 5.
Harem Hotel's 2D art style has its own charm, move to 3D with UE5 is a risky move, it's like a good hentai manga could lose its charm when it get anime adaptation or even JAV live-action version.