I don't think it's particularly .Net which slows down start-up of PE6 more that PE6 just has to do a lot more than PE5 ever did, but I cannot recall off-hand.
Linux does support Mono and that's fairly mature these days so .Net itself isn't necessarily a problem, but certain Windows specific and third-party components likely will be. It would run in a full-fat Windows Virtual Machine, but pulling PE6 out of that and running just that is the hard part, probably not possible.
We would recommend LinAXEpad or VS Code on Linux, but that does only support Basic programming, doesn't have all the frills of PE6.