Grub 2 EFI boot shows 4 more hard drives than actually installed (read error)

I have an old Macbook Pro 9,2 upgraded to 8Gb RAM and an SSD triple booting Ubuntu 21.04, Windows 10 and Mac OSX Catalina. I can boot all systems fine (except MacOS because of APFS; can boot via Macbook boot menu.), tho the windows entry for grub wont work. (can boot manually via chainloader (hd6,gpt1)/efi/Microsoft/Boot/bootmgfw.efi) Grub is installed in the First (EFI) Partition and pointed to a grub.cfg file on sda2, working fine. However when I type ls into the grub command line I get shown

(proc) (hd0) (hd1) (hd2) (hd3) (hd4) (hd5) (hd6) (hd6,gpt5) (hd6,gpt4) (hd6,gpt3) (hd6,gpt2) (hd6,gpt1) (cd0)
error: failure reading sector 0x1d190ff0 from 'hd0'.
error: failure reading sector 0x1d190f80 from 'hd0'.
error: failure reading sector 0x1d190ff0 from 'hd1'.
error: failure reading sector 0x1d190f80 from 'hd1'.
error: failure reading sector 0x1d190ff0 from 'hd2'.
error: failure reading sector 0x1d190f80 from 'hd2'.
error: failure reading sector 0x1d190ff0 from 'hd3'.
error: failure reading sector 0x1d190f80 from 'hd3'.
error: failure reading sector 0x1d190ff0 from 'hd4'.
error: failure reading sector 0x1d190f80 from 'hd4'.

sudo gdisk /dev/sda also outputs this:

MBR: protective
GPT: present

it is to be said that the partition table once was hybrid but converted back with gdisk then x then n (see man gdisk) GPT reads

Disk /dev/sda: 976773168 sectors, 465.8 GiB
Model: CT500MX500SSD1  
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 838E17FB-CAC2-4F22-ADE6-1D5671F5A858
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 976773134
Partitions will be aligned on 8-sector boundaries
Total free space is 255660013 sectors (121.9 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              40          409639   200.0 MiB   EF00  EFI System Partition
   2          411648       134629375   64.0 GiB    8300  UbuntuDisk
   3       134629376       134662143   16.0 MiB    0C01  Microsoft reserved ...
   4       134662144       232933375   46.9 GiB    0700  Basic data partition
   5       488591360       976773119   232.8 GiB   AF0A  Mac OS X

Disk Layout via gnome-disk-utility:

protective MBR reads

Number  Boot  Start Sector  End Sector   Status     Code
1                        1    97677316   primary    0xEE

where do these phantom grub disks come from and what is the correct way for either all OSes from efibootmgr (nvram) to boot with grub or show in Macbook startup selector??