Michael Tsai’s notes on the Arq 6 update:

Overall, it just seems like the app was shipped before it was ready

I still think that Arq, uniquely, gets the overall backup architecture right. Arq 6 makes major progress, but it also has some serious regressions. Most importantly, it needs more testing and refinement. I do not recommend updating right now. Arq 5 still works great. There’s no rush.

I’ve used Arq for years and it’s great, so I fully intend to upgrade. Just not right now.