For Japanese players, you'll want to get your VNs from DLSite as long as it's sold without DRM or only with PlayDRM, which works through WINE. SoftDenchi doesn't work with WINE, so don't buy VNs with that. Also, don't buy VNs from DMM, because they only sell VNs with DRM that doesn't work with WINE. Don't bother buying from Johren.
Mangagamer is one of the very few English localizers that sells a scarce few games with both the Japanese and English text intact. The games I know of that are like this are the Higurashi and Umineko series, and The Expression Amrilato. I recommend buying from them directly, rather than from Steam, because the Steam versions are hard (or impossible) to hook into with Textractor because of DRM, probably. Plus, they're cheaper on Mangagamer, and Steam doesn't like VNs. You can also buy Higurashi from GOG.
Lastly, buy physical releases because the majority of them have no DRM or use AlphaROM, which you can legally bypass by downloading a file from the DRM company on their website. Some physical releases come with DRM that doesn't work with WINE.
Also, if the files/folders are in Japanese, use unar to unarchive it. No other unarchiving tool has a 100% success rate for unarchiving Japanese-encoded text. It's designed for macOS, but some distributions also package and compile it.
In particular, they mention fjfix for その花びら novels and other furigaya VNs, which is sometimes necessary, sometimes not. It also mentions the SHIFT-JIS character encoding which is required for some novels, which I originally learned of years ago from a reddit post: https://brokendragontranslation.com/shift_jis_linux.html
For some reason, all of the files on that learnjapanese.moe page are re-hosted on Discord, and it doesn't link to the guy who developed fjfix or Broken Dragon Translations, which is kind of odd.
I really wish VNDB listed what DRM a release is encumbered with; that way, you wouldn't need to gamble when you pay for a physical release. The only decent advice I've gotten for finding out if a novel has DRM is to check on EGS: https://erogamescape.dyndns.org
I recommend running Gamescope for games you can't fullscreen, which I needed for some その花びら novels. It's a pretty cool project. It runs even on X.org with a NVIDIA card. The easiest way I found to run Gamescope is to integrate it with Lutris. Cheers to Valve and Sourcehut for developing Gamescope.
That's all for just running VNs. If you're also learning Japanese, here are some additional tips:
Install Yomichan and a bunch of dictionaries.
Install Anki and AnkiConnect to make cards quickly.
animecards.site has a pretty good guide for setting up Anki cards you extract from your VNs.
Install your VNs in a WINE prefix and install Textractor in the same WINE prefix.
Install transformers_ocr to OCR text from VNs if you're running them natively or can't hook into them with Textractor. There's Kamui's Gazou as well, which is also based on Tesseract, but I think transformers_ocr is simpler and easier to use.
Install ames to quickly export audio/images from your VN to your Anki cards.
Happy if it helps! It's kind of sad that so much of "getting VNs working" involves cataloguing different flavors of DRM and whether they work through WINE. What I wouldn't give for a database of "this release's DRM works through WINE".
I doubt Valve will ever put any money toward getting these particular brands of DRM working through Proton because <1% of Japanese VN publishers publish their games on Steam, and Valve seems to want to distance themselves from the image of VNs anyway. It's almost entirely localizers publishing on Steam.
They're kind of in a war with The Moe Way (TMW)/learnjapanese.moe...I don't know the finer details, but Tatsumoto has taken some information from their site and republished it on his site, pretending it's his own. Tatsumoto also pinched commits from TMW's fork of Yomichan for his own fork—which is perfectly okay, it's free software, but he doesn't seem to have added much himself and seems to have given up on it for now.
I don't really think TMW has much of a leg to stand on considering how much they encourage copyright infringement of other people's stuff over there, but it's worth mentioning TMW community produces a lot of cool software, just as Tatsumoto does.
Things get weird sometimes, but both communities have a lot of useful stuff, so it's worth perusing their websites.
Some people at Valve really don't like high school settings also being eroges, and I don't think I can blame them seeing as how the liability would pretty much all be on them for distributing.
I don't think Valve is wrong to have standards, and these particular standards make sense. My issue is with how they communicate with publishers. See JAST's statement on Muramasa, for example: https://jastusa.com/page/the-state-of-muramasa
Our case is, unfortunately, not unique in the industry. An increasing number of visual novel games are getting unjustly banned from Steam, with no recourse. This creates an environment where publishers don’t release games like Muramasa because the risk is too high with Steam's heavy-handed hold on the PC market, stifling the medium and forcing publishers to adopt self-censorship to survive.
It seems like JAST is not entirely sure why Valve is firm in barring Muramasa from their platform. I suppose they could be deliberately withholding that information, but it seems unlikely.
Muramasa is not set in high school and clearly isn't indulging in or glorifying sex/violence/sexual violence, and it doesn't seem like Valve has much of an issue with explicit sexual content given how easily I ran into games like Being a Dik without even searching for it, among hundreds of other 18+, sex-heavy games.
The experience is pretty awful for players. You get releases like Subarashiki Hibi, where 10% of the game is available on Steam, and you need to download the patch from the publisher's website. At that point, why bother buying the game on Steam? Why not just buy it directly from the publisher?
It's unfortunate. Valve could make it easy for publishers for being very specific about what content they do not want to see, and what would need to be stripped out, and whether off-site patches can be offered for the offending content. It seems like publishers are just guessing what might set off Valve's alarms.
Yeah, the real issue is the inconsistency in which those standards are applied over at Valve. I believe it has been at least guessed at that there are more than a few puritans on staff applying stricter-than-required scrutiny on visual novels specifically, but don't remember the source for this claim.
On the one hand, it wouldn't surprise me if that were the case, but Valve is usually known for their lack of action or direct opinions. Either way, it seems unlikely this will change any time soon.
People Make Games covers how Valve feels about pornographic content and other sorts of questionable content in this section of their video and why they are so staunchly against being specific about the content they don't want on their platform: https://youtube.com/watch?v=s9aCwCKgkLo&t=35m41s