...I just did a search of the Arduino IDE repository to see what had been said on the subject and there are some things you might find of interest in the results:https://github.com/arduino/Arduino/issues?q=rs485
If you have any questions on using GitHub I'm happy to help. There's a little bit of learning curve but I think you'll find it worthwhile in the long term. It's by far the most popular site for hosting code now and they really do a great job of making it easy to collaborate on open source projects. If you're already familiar with Git version control then you already know most of what you need to use GitHub. If you aren't familiar with Git then the basic concepts you need to learn to be able to use GitHub will be a useful introduction. I started with GitHub because I had a couple bugfixes I wanted to submit to some Arduino library repositories. That eventually got me started on using Git version control on my own projects and it has made a huge difference in the quality and efficiency of my programming. I'm sure it's not for everyone but definitely at least worth giving some consideration.
There was also some issues or pull requests in those search results regarding modifying HardwareSerial for use with RS485. I didn't read them very thoroughly but thought they might be relevant.I think it's good for people to have multiple choices. Every user has different needs so it's difficult for one one library to work for everyone. There's certainly no need for there to only be one Arduino project for each application.Did you get any insights on how that library had dealt with the issue of HardwareSerial and the interrupts?