You wouldn't break much. The only thing that stops working outright is grub-btrfs (Timeshift snapshots as boot entries — tied to GRUB by definition), and Soplos GRUB Editor, which obviously becomes pointless.

Dracut isn't affected. It only generates the initramfs, independent of the bootloader — if anything the integration is more natural with systemd-boot via kernel-install.

One thing worth knowing since you asked about every update: our soplos-release package (the version-identity package, updated frequently) runs update-grub in its postinst, guarded by command -v update-grub. If you fully purge the GRUB packages when switching, that check just fails cleanly and the step is skipped — no error, no broken update. If you instead keep the GRUB packages installed alongside systemd-boot, that hook will keep quietly running update-grub on every soplos-release update, rewriting a grub.cfg nothing reads — harmless, just wasted work.

Also keep in mind our tools (Soplos Welcome, Kernel Installer) write kernel parameters to /etc/default/grub — e.g. nvidia-drm.modeset=1 when installing NVIDIA drivers. With systemd-boot that file goes unread, so you'd need to add those parameters manually to your boot entry.

Other than that, updates won't give you trouble either way.