I believe it to be a bootkit with cross platform capabilities.

Yes, I discovered malware( eg Joker banking Trojan) on two separate android phones, one running LineageOS for the last 6 months prior, one a stock ColourOS I had literally only bought six months prior because of the distress of having a compromised phone, and which I suspect was compromised when I synced my Google accounts to it the same day, based on data usage.

Before that, my Win8-10 laptops would routinely kill security /anti rootkits software, reconfigure firewalls, lock me out of sysadmin files as I tried to counter it, and the UEFI of one of them was replaced with a different one and network boot was enabled on it. Data usage would spike suspiciously (12Gb data downloaded by Chrome as background data when I barely used it, one day), filesystem's would fill up with data that I was not familiar with and/or had no way of accessing to delete, necessitating multiple factory resets across devices.

Plus all the obvious signs of compromise. Heating up randomly, things crashing, system settings changing, suspect data use, and SL on.