Eh, I don't blame the solo developer. Official Linux support would be nice, but it's still only used by 2% of Steam customers, most of which are on the Steam Deck:

https://store.steampowered.com/hwsurvey/Steam-Hardware-Software-Survey-Welcome-to-Steam

There is a non-trivial amount of work involved in creating and supporting Linux binaries. Based on what other developers have reported, despite the small number of Linux users, they can be responsible for a disproportionate number of support tickets. I think part of the reason for this is has to be the enormous number of Linux distributions out there. While most users are using a small handful of distros and their derivatives, there's just too much variety within a very small portion of the market (plus the whole issue of poor GPU driver support on top), which can lead to all sorts of unexpected and difficult to replicate compatibility and stability issues.

Not to mention, this game is playable on the Steam Deck. It seems to work just fine on Linux (or at least Arch) through Proton, so why complain?