It looks like dayz is gold, rather than platinum, meaning it will take a little tinkering. https://www.protondb.com/app/221100

Usually I start debugging this type of thing by killing all instances of steam and then launching it from command line. Steam logs a bunch of good stuff and putting it in context of your interactions helps. That said, based on what you’ve described, I would try older versions of proton, targeting releases back when games were launching. Proton/wine versions don’t always work for all games and sometimes you’ll need to launch particular titles with specific versions. Proton has been absolutely revolutionary, but these issues still pop up. ProtonDB might have reports on specific versions for specific games/titles.

The problems you describe are due to capitalism: profit motivated commerce. The open source business model has a focus that monetizes the human actions that are a value-add, such as continued development of targeted features, tech support and other things it makes sense to pay for specialized knowledge, but the tangibles are still open for all to modify, audit or use as they want.