A question of how – Mount, Find & Recover DATA in HDD outside of Synology Box
[With] a Synology … run into issues or Hard Drive corruption/ error in sectors etc. where I have had to pretty much remove the Drive which Synology refuses to read or work with. The question is, assuming I am able to detect the Hard Drive and assuming that hardware is still kind of functional, what way can I LOAD/ MOUNT the Drive (under Windows or Linux OS etc) on a PC/Laptop? (What tools/ software should I used to do that?)
Home NAS Recovery will work for you. Syngle-disk Synology is pretty standard setup. I have to recommend a PC, not a laptop. When the drive is suspected to have bad blocks, the common wisdom is that USB is to be avoided, and laptops are mostly limited to USB.
I’ve used several Partition Management tools and I can see 4 partitions inside the Disk as created by Synology.
That’s normal, and does not provide any significant additional information.
[various ext4 reading programs] none of which have been able to recover data (geeksnerds, stellar phoenix, linux reader, explore2fs, ext2explore, none of which allowed me to copy, recover or even see data files).
That depends on how bad the disk is damaged. Also some of these programs may be not quite compatible, especially if we are talking about modern Synology with EXT4. While EXT3 is identical to EXT2 in all respects concerning read-only driver, EXT4 is different.
[also] a Linux / RAID based solution that worked for someone, but not for me.
If Synology with its own, specifically adapted Linux, refused the disk, then most likely any stock Linux distro will also refuse the disk.