TraceyC
dear Tracey,
i just re-installed Manjaro again.
It uses the same Calamares installer as Solus.
Because Solus was installed falsely as GPT on the HDD one hour ago, the similiar Solus-installation-pic from before now said BIOS + GPT.
But even though the Manjaro-installer recognised it as GPT: the Manjaro-installer created a MSDOS - Partition Table on the Master Boot Record.
All this in the summary and during installation.
my laptop is now bootable with Manjaro and its Grub, and all works.
it seems the Manjaro-installer is more correct in choosing the format of the partition table (MSDOS or GPT), while the Solus-installer seems to always choose GPT.
...and i still have no idea how i could install Solus successfully.