I’m not aware of any support for Trim on the UHS interface either. If you find anything definitive I’d love to read it (I expect you won’t but happy to be proved wrong).

Thinking about it, I wouldn’t be surprised at all if a third party was selling software purporting to run Trim commands on SD cards, but if so you can almost certainly file these in the same snake-oil BS category as RAM doublers (remember those?) and SSD defragmenters.

As I said before, Trim is a feature on AHCI interfaces (and SAS but let’s ignore that for simplicity). Ie, it needs to be a SATA SSD connected to a SATA interface in AHCI mode. This is the same reason why you can’t Trim an SSD in an external USB caddy – although it’s an SSD, you’re not attached to an AHCI-capable interface, you’re attached to the USB interface, so no Trim.

Ah, is this what you’re thinking of?

https://en.wikipedia.org/wiki/Trim_(computing)#SD.2FMMC

The… SD ERASE (CMD38) command provides similar functionality to the ATA TRIM command, although it requires that erased blocks be overwritten with either zeroes or ones.

I don’t know whether it’s a mandatory feature of the SD command set, but I can see how lock erase support could theoretically vary from card to card.

EDIT: it is mandatory, I’ve just looked it up. So it’s a non-issue anyway so long as manufacturers adhere to spec. It was an interesting aside (relevant discussion here), thanks for that.