Rumour has it that there is some PDF/A capable library for .NET, but I would have to put in quite some time to figure out if it is low level enough for the control I need and whether there are additional libraries suited for layout and typography. Since I might have to ditch it within five years, that's not an option.
Some people claim .NET developer ergonomics on Linux are fine now, but those I know personally that tells me this are using VSCode, which I consider a rather shoddy piece of software. Am I going to take the time and see if it's the case? Fiddle around with IntelliJ plugins and try to setup a LSP for vim and whatnot? Nope, I won't, because there is no revenue in that, and I might suddenly have to do the great rewrite several times at once further down the line.
Maven is a turd, but a very solid one when you've figured out the XML incantation you need. I'm not sure what the alternatives are in .NET-land, or whether I can feel that I trust that they will work fine in ten years, like fifteen year old Maven projects tend to do. GraalVM allows me to output neat executables too.
Java has Wildfly. What's the equivalent in .NET? Running a MICROS~1 Windows Server with IIS? That's not an option.
And so on and so on.