I thoroughly enjoyed the original game Subnautica, and have previously skipped the semi-sequel Subnautica: Below Zero (commonly and hence "BZ" when I feel like it) because of predominantly bad reviews from people who were disappointed that it wasn't more like the original. I'm happy to report that while their complaints are not unfounded, they don't make it not worth playing - and also that you can have a satisfying experience on Linux.
Briefly, and hopefully without too many spoilers, Subnautica is a mostly sub-aquatic crafting/building alien planet exploration survival game with a big submarine, and BZ is a maybe-sequel-maybe-spinoff which takes place on the same planet and which only has a small submarine to which modules attach and make it bigger and goofier. Both games run in the same engine, both are nice to look at, and both have modest system requirements by modern standards.
My system is now running Devuan Linux, with Nvidia CUDA and drivers installed from the runfile, and Steam installed from the deb. Long story short, the runfile drivers are most compatible with the Multiarch needed for native Steam (and for other purposes, like 32-bit Wine.) I have an AMD 5600X on an ASRock B550M Riptide PG, with 64GB RAM and an Nvidia 4060 Ti 16GB. This is sufficient to run this game at a solid 60 FPS or better (but my 4k TV is limited to 60Hz) at 4k with everything turned up to the max. I played the original on an AMD 1600AF and Nvidia 1070 at 1080p60, with similar results.
I chose to run the game from Steam under Proton-GE 9.10, and it runs very well. It was recently on sale there for $14.95, which I'd say is a fairly reasonable amount to spend on it. The normal price is $29.99, which I don't think I'd feel good about paying at this late date.
I chose to build a base at the Twisty Bridges and found that I couldn't build parts of it as I wanted despite it looking like there was plenty of room. This irritated me enough to want to mod the game, which turned out to be its own irritant. Luckily, some nice people over at Nexusmods have recently done most of the hard stuff, and you only need to know which mods to install. These instructions apply to the 2022 version of the game; it may well be that only some or even none of this stuff works on some future version. Also, this is not an instruction for how to install every possible mod, it's just to fix problems and make a few "QoL" (Quality of Life) improvements. I'm not trying to change the game completely, just make it a little more enjoyable.
Tobey's Pack
First, you will want to start out with Tobey's BepInEx Pack for Subnautica Below Zero. This provides mod support for Windows, Linux, and Macintosh users. If you would like to use Vortex Mod Manager there is support for that, but I just installed all of the mods by hand. These mods are small enough to where installing them is not very complicated, though you have to do a little bit of strategic unpacking of a zip archive for one step. To get at the install directory easily, right-click the game in your steam library list and open the Properties, then click Installed Files followed by the Browse... button. To manually install the pack, you only need to do two things: One, unpack it into the game directory. Two, tell Proton to load the winhttp.dll from the pack by setting the launch options in the Steam properties to this:
WINEDLLOVERRIDES="winhttp=n,b" %command%
Installing that pack will not have made any visible changes to the game. It's really just getting BZ ready for mods.
QModManager
The other possible part of getting BZ ready to go is installing QModManager. Not every mod requires QModManager, but some do. If you install it following the directions that come with it, you will downgrade BepInEx from the version which comes with the pack you installed in the prior step. But that is not necessary - it does work with that version and install without messing it up if you install it manually like so: Open up the archive with some archive manager (I am using lxqt-archiver) or unzip it to a temp directory. Inside you will find a BepInEx directory, inside of which there are four directories. Copy the contents of just the patchers and plugins directories into the corresponding places in the BepInEx directory that was created in the game directory when you installed the pack above. Now there will be a Mods option in the settings to control settings for some QMods. Running the game once with it installed should create a QMods directory in the game directory; if it doesn't, you can create it manually.
SML Helper
SML Helper Zero is another requirement for many mods. The files in its zip archive have backslashes built into them, which might or might not work correctly on Windows but which produced files with backslashes in the names instead when I unpacked them on Linux. Make a new directory in QMods called SMLHelper_BZ and unpack SML Helper Zero into it. Then rename the files to take the "SMLHelper_BZ\" out of the filenames.
That's the last of the weird stuff. There's just one more prerequisite: VersionChecker is another common requirement, which requires QModManager. If you need it, after installing QModManager, put its directory into QMods. BepInEx mods are in general installed the same way as QmodManager. Many or even most mods also have instructions for manual installation; you can install them just the same as you would on Windows.
The rest of this article is where we actually get to the mods I wanted to install. You could install some or all of these; if you only install any of the first few of them (the BepInEx mods) you only need to do the first part of the setup steps above (installing Tobey's BZ pack.) QModManager and SML Helper are now abandoned software, and it is possible that future game updates will break them and nobody will fix them.
BepInEx Mods
- Fast Loading Screen speeds up loading by disconnecting some operations during load time from the frame rate.
- Subnautica Autosave BZ (Official) is the autosave mod that still works correctly. The other one (just called "Autosave") prevented me from opening the save menu.
- Building Tweaks allows you to disable most of the rules preventing you from building things wherever you want by pressing "G". It also allows you to break down structures you otherwise couldn't.
QMods
- Respawning Creatures allows more of the fish and whatnot to respawn after you eat them than would normally do so. You can disable leviathan respawning, which I think is fair: Change the contents of the mod's settings.json file to
{"leviathansRespawn":false} - Aeyos' Quality of Life Improvements (which also requires SML Helper) which allows you to build things where they normally wouldn't be allowed because they are too close to something else, re-enables achievements even when the game is modded, and lets you open containers with labels even by clicking on the label (with a configurable key to disable that.)