Edit: sorry, I may have misunderstood your post - free email != email masking.
My original post below…
Curious why you consider email address masking services as for those with “drastic anonymity” requirements?
I personally don’t think so: they are pretty much just a digital P.O. box, and are typically not anonymous in any way (subpoena/court order to the provider). They are built-in to Firefox too, it will automatically create new ones OOTB as you sign up on websites, if you click the autofill.
They are however IMO one effective tool out of many to restrict the ability of data brokers and hacking groups (aggregated breach datasets) alike from making money from your online presence without your consent.
In almost all cases this data is freely searchable for law enforcement and private investigators, allowing them to avoid going through the legal system to investigate and possibly detain you for things you’re not guilty of
Flash drive hidden under the carpet and connected via a USB extension, holding the decryption keys - threat model is a robber making off with the hard drives and gear, where the data just needs to be useless or inaccessible to others.
There’s a script in the initramfs which looks for the flash drive, and passes the decryption key on it to cryptsetup, which then kicks off the rest of the boot mounting the filesystems underneath the luks
I could technically remove the flash drive after boot as the system is on a UPS, but I like the ability to reboot remotely without too much hassle.
What I’d like to do in future would be to implement something more robust with a hardware device requiring 2FA. I’m not familiar with low level hardware security at all though, so the current setup will do fine for the time being!