Later Edit: It seems there's an issue with the Imager on Linux Mint, although Mint is based on Ubuntu. Installing the OS using the command line as described here worked flawlessly
Image Writer: Raspberry Pi Imager 1.4 running on Linux Mint 20
SD Card: 64GB Adata
Raspberry Pi: Rasberry Pi 4 B. 4GB of RAM
Image OS: Raspbian Lite (no desktop enviroment)
I'm trying to write the OS file on the SD card and enable the ssh via the ssh file in the boot partition.
However, when I try to create the ssh file in the boot partition, I get an error because the filesystem is read only.
Writing Ubuntu Server 20.10 to the same disk doesn't seem to have that issue. My feeling is that it has to do with the size of the disk as the same process on an old 8GB SD card seems to be working flawlesly.
I'm excluding a faulty SD card as formatting it using Mint's Gparted is making the card writable again.