Other than having to reload a replay to get out of the 1st person spectator cam it runs quite nice on 1.18 with mods, data packs, and resource packs. There might be some kind of memory spike bug where loading the same replay and single play world server chews up memory usage and causes Minecraft to crash but it could also have been too many mods, data packs, and resource packs causing an incompatibility. That's about it. Needs some polish and performance enhancement but getting stuck in 1st person until I reload is my only real issue on 1.18.2

hotkey unbound/unbindable

The key to leave the first person mode (Sneak) is the same key as in the vanilla spectator mode. It should neither be unbound nor unbindable, nor do I even know how you'd determine that it was unbindable (the vanilla game doesn't have a concept of unbound yet unbindable hotkeys).

That's simple to answer because my (Sneak) is not bound to the vanilla sneak key-bind and after trying every key on the keyboard I still was not able to exit first person mode without closing the render and reloading the saved file. Thus why I created an issue to notify you that it was impossible, at least for me, to get out of first person mode after going into first person mode. I apologize for not responding earlier but this is how I determined that it was "unbindable" and if the vanilla game doesn't have a concept of unbound yet unbindable hotkeys why is there a hotkey configuration list in the options menu tabs? I am very confused by your response.

Edit: Oh whoops I misspoke while not remembering "the vanilla spectator mode" but i don't use spectator mode because a mod I use has a simple free-cam feature in survival... When I have time I'll switch my mod list back to 1.18 and see if the vanilla spectator mode hotkey takes me out of first person mode... Although I'm pretty sure I tried every single key on my keyboard after running into this issue!