Players using 32-bit Windows PCs can still play the latest version of Unturned in single-player. However, multiplayer requires using an older game version.
The final version of Unturned with multiplayer support on 32-bit Windows was v3.22.14.0, released on August 12, 2022. This version is still available through Steam's Game Versions & Betas feature on the "32bit-windows" branch.
To play multiplayer on this version, you'll need to install it on a dedicated server and have all players download the same game version. For more details, see our article on playing older versions: Older game versions & beta branches.