Quick search surfaced the following for Linux:
k3b, where the source repo states bluray burning capabilities.
xfburn also mentions bluray burning capabilities.
For Windows, albeit old and unupdated, I know the following still works for other purposes (never tried bluray burning/writing though):
ImgBurn mentions bluray burning/writing capabilities, but never tried it.
Bonus: not capable of bluray burning/writing but just fun to mention for any still into ripping/writing to discs on Windows:
InfraRecorder, simply a classic, and it’s open source!
“Behold, I’m a unicorn!”