Upgraded from a 2011 Mac mini to a M1 Mac min (8/256). Installation and migration was smooth and quick.
Took the 2TB (media and music) second drive out of the old mini and put it in a decent external enclosure. Decided to start with new Music and TV libraries. Importing my music from an another external drive kept failing at random points with errors such as "file name too long" or "file not found", however retrying with the same files would work. Eventually finished and seems OK.
The TV library however wasn't so smooth, lots of lost artwork which I had to manually add.
Biggest issue is iFlicks, it seems to convert MKV to MP4 OK but adding to "iTunes" step never completes. I've had to turn off that option and manually import the converted files.
UPDATE:
It turns out it wasn't iFlicks fault at all. When I checked the transfer speed of the external hard drive where the TV library was hosted, I was only getting a shade over 30MB/s! After doing some troubleshooting it turned out that USB-C to USB-C cable (a brand new UGREEN flat cable) was restricting the speed, when I switched to another UGREEN cable the speed increased to over 130MB/s, not spectacular but a great improvement. This speed is limited due to the 2TB HDD I'm currently using, I put an old 250GB SSD in the enclosure (as a test), I could get close to 300MB/s.
After getting an 4 times increase in speed, iFlicks now seems to able to complete adding to the TV library.
So I've ordered a Samsung 970 EVO 1 TB PCIe NVMe M.2 blade and an ORICO USB 3.1 Type-C to M.2 NVMe SSD Enclosure to host the TV library and I'll probably get a 1TB SSD for the existing enclosure to host the Music library.
UPDATE 2:
Copied the TV library to the new external disk and it flies when adding to TV library. I'm getting better than 900MB/s write speed now, a 30 times improvement!