AC # 53068 does not come up as a valid part number on the Aquacomputer store site. There is a High Flow LT (#53291) and a High Flow 2 (#53292) but no "High Flow". I suspect the High Flow is discontinued and no longer available. The Owner's Manual for the Aquastream Ultimate pump only lists support for the "Flow sensor with 5.6mm nozzle" #53061 and the High Flow #53068. The Farbwerk360 Owner's Manual lists support for the same 2 flow sensors plus the High Flow LT (#53291) and the High Flow 2 (#53292). I think this is due to when these products were released. The newer High Flow Next is USB based and reports directly to Aquasuite. It does not have a 3-pin Flow output connector so there is no way to plug it into the Flow port on the Aquastream Ultimate or the Farbwerk360.

You said when you pick any of the flow sensor models in the pull-down menu, you get weird values. Do you have something plugged into the 3-pin Flow port on the Aquastream Ultimate or the Farbwerk360 when you are getting these strange values? If nothing is plugged into those Flow ports, it seems to me that the reading should be zero.

I may be confused so apologies.

I understand that the High Flow Next is the newest, most advanced model, but I don't have a High Flow Next (yet) so my statements about it not having a Flow connector were based on Internet pics and the Owner's Manual. AFAIK the High Flow Next has headers for USB, Temp, RGBpx, Signal, and Aquabus. There is no header named "Flow" but you are correct that the Signal header can be used with cable #53294 to connect to a PWM port or with cable #53295 to connect to a "flow sensor input on Aquacomputer devices". Based on this, it would seem that you could connect the Signal header of the High Flow Next to the Flow header of a Farbwerk360 or the Aquastream Ultimate pump, but the Owner's Manual for both of these devices do not list the High Flow Next in the Connector - "Flow" section of their manuals. They only list the older flow sensors. The Aquastream Ultimate lists the 5.6mm Nozzle Flow Sensor #53061 and the High Flow #53068 (both discontinued?). The Farbwerk360 lists these 2 plus the High Flow LT #53291 and the High Flow 2 #53292. Neither of them lists the High Flow Next #53293.

Since the High Flow Next is not listed as compatible in either Owner's Manual, and you said that it is not available in the pull down menus and you get crazy readings, it seems that it is not compatible with the Flow inputs on these devices. Also note that the High Flow Next lists cable #53295 (miniature connector for Flow headers). The Farbwerk360 manual lists cable #53212 for the 5.6mm Nozzle flow sensor and the High Flow but does not list cables for the High Flow LT or the High Flow 2. The Aquastream Ultimate manual lists cables #53027 and #53100 but does not specify which cable is for which flow sensor. Neither of them list cable #53295 which is the cable that the High Flow Next manual lists for connecting to an Aquacomputer device with a Flow sensor input header. This is confusing to me. To add to the confusion, based on cable #53027, I think the Flow header on a D5 Next is a different connector than on the Farbwerk360 or the Quadro / Octo. I also do not have a D5 Next (yet) and have yet to find a clear picture showing all of the connectors on it so I am not 100% sure about this.

Regarding the status of the High Flow 2 and High Flow LT, I don't know if they are discontinued or not. The part numbers both come up in a search on the Aquacomputer online store. The High Flow LT shows in stock. The High Flow 2 shows out of stock with delivery times up to 60 days which is the same status as the High Flow Next. This leads me to believe that the High Flow LT and High Flow 2 are not discontinued. The part numbers for the High Flow #53068 and cable #53100 do not come up in the search box iin the online store at all.

the high flow 2 came out with the High flow next, it's part of the new line of flowmeters, so it's very much current.
I believe the high flow LT is just a less expensive version of it.