HDD or SSD for Time Machine

HDDs are "best" for doing backups and what I would recommend you go with for Time Machine ... and for the following reasons:

• Larger capacities at a lower price point that SSDs.
• HDDs are still the industry standard for file storage / backups.
• You don't need a "fast" HDD for backups. A 5400 rpm drive will be more than adequate. "Red" drives, that are designed for this purpose would be the better choice.
• SSD drives have one major disadvantage over HDDs. That is, their individual storage cells, are write limited. Reading from SSDs do not wear them out, but writing to them does. Most SSDs are rated by their respective manufacturers for how my write cycles they have before becoming unusable.

FWIW, I basically have the same M2 Pro Mac mini, but only differ in that its internal drive is a 1TB SSD. For Time Machine, I use three different storage devices:

1. A Synology DS916+ NAS (HDDs only). My NAS uses four WD "Red" HDDs. << The current equivalent to this model is the DS923+
2. A Western Digital My Book Pro (HDDs only) << WD no longer sells these, but now offer the My Book Duo. My Book Pro is equipped with two WD "Red" HDDs.
3. A OWC miniStack STX (HDD & SSD) << I only use the HDD portion for TM.

HDD for Time Machine is fine if you are not restoring files from the backup every so often, because if you do, you will find the speed to be a tad frustrating.

SSD for images, specially if you edit your images, is best.

I don't have specific HDD recommendations, but you may find the Lacie, Western Digital, and Seagate to be pretty good brands.

It won't hurt to use an SSD for Time Machine backups.......but it also won't help, since Apple limits backup speed and restore speeds with Time Machine.