I have had the best long-term success with LaCie drives (mainly RAIDs), though I think their overall quality has dropped in recent years. I would think that an external SSD should be really reliable, but I don’t have any experience with them so can’t say for sure. Steve is likely to have much better suggestions.
My main iMac has three external drives right now. Two are LaCie RAIDS, the other is a LaCIE non-RAID. Each has been working more or less without problem for years.
I've used OWC drives for several years and they've been reliable but can get loud. I do have a SanDisk 1TB external SSD drive, it's great if you can get by with 1TB.
SteveBob atropos