So I have both a MiniDSP Flex 8 (a balanced eight channel device that's very similar to the Flex HT) and a MiniDSP 2x4HD. I've been very very happy with the MiniDSP Flex 8. It really is set and forget and is a nice low noise device that's easy to interact with. If you only need USB inputs and don't need HDMI or analog inputs, you might want to consider the Flex 8 instead of the HTx (it's cheaper, and the main difference is that the Flex 8 only has USB and bluetooth inputs).
The 2x4HD worked well for more than a year, but eventually developed an intermittent power fault (where the power supply connects to the box) that would put the box into a failed state and require a restart every so often. I had to replace the unit and the replacement worked fine, but it was out of warranty, which was irritating. The replacement has worked fine since then. That was an older MiniDSP design though, the Flex's are all newer and seem to have a much nicer build quality.
The only downside from my perspective is that the device programming/control software is Windows only. To be clear, you can use them as audio interfaces just fine on Linux, but programming them officially requires a Windows PC (although there is some open source unofficial software for programming them on Linux, but I haven't tested it and it's a little rudimentary at this point). If you run only on Windows this won't affect you.
I saw that you don't want anything from Topping but I know that a few JRiver users have the Topping DM7 (I'm one of them) and love it.
https://www.topping.audio/productinfo/862560.html
It has USB audio, 8 channels, and balanced TRS outs that could easily be adapted to XLR. It can also be adapted to unbalanced RCAs (I don't have balanced amps). The forum thread related to this is https://yabb.jriver.com/interact/index.php/topic,134316.0.html
I also have a Topping DM-7 and am very happy with it. I actually use it on the same system that I use the MiniDSP Flex 8 with as both have 8 channels that I need for my active bi-amped speakers and subs (JRiver connects to the Topping so it can control it fully and take advantage of JRiver's superior DSP, and system/web audio goes to the Flex 8, which has good enough DSP for video games and youtube).
Another option could be the Okto Dac8pro if available
https://www.oktoresearch.com/dac8pro.htm
These seem very hard to come by. I've never seen them for sale directly from the manufacturer whenever I've been in the market. Maybe I'm just unlucky