Here are makemkvcon syntax parameters for you to try: https://bluray.beandog.org/makemkv/man/makemkvcon.html
I believe they do. Their Linux installer link is buried in the forums: https://forum.makemkv.com/forum/viewtopic.php?f=3&t=224
They have batch ISO convert CLI for Windows: https://forum.makemkv.com/forum/viewtopic.php?f=10&t=15426
You may need to network share your headless seedbox or whatever you have the ISO on to do this off a linux or Windows machine.
AirVPN has a number of Linux options running through openVPN or wireguard https://airvpn.org/linux/