You can still play the newest versions of Unturned in singleplayer on a 32-bit Windows PC.
The final version with multiplayer support for 32-bit Windows was 184.108.40.206 released 2022-08-12. This version is archived on the 32bit-windows Steam beta branch. If you would like to play multiplayer on this version you can install it on a dedicated server and get your friends to install it as well. See this article for more information on playing older versions.