I do not remember, if grub or bootctl is being used; at least the latter command is found. But is it not typical to get grub on a headless ARM server? Is there a way to find - when arch-chroot into it - if it uses bootctl or grub? (step 1)
The partition layout is such:
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 411647 409600 200M c W95 FAT32 (LBA)
/dev/sdb2 411648 62333951 61922304 29,5G 83 Linux
gparted says that out of the 200MiB 170MiB is used. Should that point to a size problem and it just needs an older kernel (which?) deleted?
Neither One. On ARM devices, a bootloader takes the place of grub and systemd-boot. The most common one is u-boot and another is tow-boot.
To install EnOS ARM on an ARM device, one downloads a tar image or a bit-by-bit image and burns the image onto a storage device. The boot partition size is determined by the script that creates the images. So one would have to do a git clone to download the script, then edit the script manually before running it to creating an image.
I have never seen the boot size cause any problems on EnOS ARM devices.