I'm of the opinion that SNAP and Flatpack are just different Linux distributions and should package their own software like other distros do. Trying to get upstream to build for these is IMHO not appropriate. When upstream starts needing keys and crap to push builds into a central location/store it's gone way too far - you're burdening upstream and for what?
BTW the easiest way to run Solvespace on Windows is to download the single-exe build. Where I work this is easier than using winget because the exe will run without admin privileges while installing from winget requires it.
No, they don't need to do anything. This is open source software, provided at no cost to the user. The user is not owed a damn thing.
Now a maintainer may choose to provide a build or easy-to-use installer, because making things easier for users (which will presumably increase their user base). They might do that because that has value to them, they find it fun an interesting, they want to feel pride that they have a lot of users... etc.
But they don't "need" to do anything.
Not sure why that triggers people.