Boot method: SD-card via USB 2.0 cardreader
Image version: https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-10.10.0-amd64-netinst.iso
Date: 10th July 2021 10:00

Machine: MSI B75MA-P45
Processor: Intel(R) Core(TM) i7-2600 CPU
Memory: 12288 MB 1333 MHz
Partitions: See added logs.

Output of lspci -knn (or lspci -nn): Probably see added logs as well.

Base System Installation Checklist:
[O] = OK, [E] = Error (please elaborate below), [ ] = didn't try it

Initial boot:           [O]
Detect network card:    [O]
Configure network:      [O]
Detect CD:              [O]
Load installer modules: [O]
Detect hard drives:     [O]
Partition hard drives:  [O]
Install base system:    [O]
Clock/timezone setup:   [O]
User/password setup:    [O]
Install tasks:          [O]
Install boot loader:    [E]
Overall install:        [E]

Comments/Problems:

Installation fail with: "Unable to install GRUB in dummy
Executing 'grub-install dummy' failed.
This is a fatal error."
My goal was to install Debian on a BTRFS partition with compression enabled. The wiki mentioned some limitations with booting BTRFS with compression (thought only on RAID 1), so I made a separate /boot partition.

I just tried installing without changing the default partition table and
just telling the installer to use the whole disk. Also fails on
installing grub, but this time with a slightly different error message.
See the attached logs.

Hi Julian,
piece is:

Jul 10 09:41:19 in-target: grub-install: Warnung: Cannot read EFI Boot* variables.^M
Jul 10 09:41:19 in-target: grub-install: Warnung: read_file: could not read from file: Eingabe-/Ausgabefehler.^M
Jul 10 09:41:19 in-target: grub-install: Warnung: vars_get_variable: read_file(/sys/firmware/efi/vars/Boot0007-8be4df61-93ca-11d2-aa0d-00e098032b8c/raw_var) failed: Eingabe-/Ausgabefehler.^M
Jul 10 09:41:19 in-target: grub-install: Warnung: efi_get_variable: ops->get_variable failed: Eingabe-/Ausgabefehler.^M
Jul 10 09:41:19 in-target: grub-install: Fehler: failed to register the EFI boot entry: Eingabe-/Ausgabefehler.^M
Jul 10 09:41:19 in-target: Failed: grub-install --target=x86_64-efi  ^M

This is odd behaviour - your system identified OK as UEFI earlier, but
the grub-install command is failing to even *read* the UEFI boot
variables. I've never seen that happen before. I'm hoping that our
main Grub maintainer Colin can follow this a little further...