Hello,
I had a little trouble getting Systemd-boot to work with Mint in multiboot, but in single-boot the problem is identical.
The package to use is sicherboot, it is officially designed to run a Secure-boot system under mint. But it works just as well on a system where Secure-boot is disabled. It creates boot-loader entries and updates them when the kernel is updated.
Under Mint, the systemd-boot package doesn’t exist as such, it’s sicherboot that supposedly installs systemd-boot…
Under Sid, the systemd-boot package works “out of the box”, updating entries without any problem, although this was not the case in the past, when a script had to be created for this job.
I hope this information will be useful for some of you.
In the meantime, I’ve got rid of grub completely 
I don’t need that big thing just to get started…
