Using the link above, I flashed SD cards with 1.6r1-eu025-us and 1.6r1-eu026-us. I am not certain my version of -eu025 was the exact one you were using, because mine had the "-us" suffix on the filename, and the page I got it from (see above) indicated a release date of Jul 1 (2021).
iFly connected to the Stratux (a Pi 3B, btw) running both versions (I used AUTO-DETECT), and showed nearby traffic. I was also logged into the Stratux GUI from a different device and saw all the same traffic info via that interface.
There was one oddity in behavior that I noticed, but it did not seem to affect perfromance. My original 1.4r5 version and the 1.6r1-eu026-us looked the same when I went to Menu > About > Connected devices. Both presented a window that looked like this:
However, the 1.6r1-eu025-us version presented a different look:
All three versions looked the same when I checked the connection status via Menu > Setup > ADS/B. This different look seemed to be consistently repeatable--I booted each version at least twice and -025 was always the oddball. EDIT: Hm. I just got this behavior with -026, too, so apparently it's not unique to -025.
The only other difference I noted was that it felt like it took a long time for the -026 version to boot the first time. Long enough that I started to suspect a bad card or a bad flash, and was in the process of reflashing one of the other cards with -026 when it finally finished booting (as indicated by the brief fan spin and the appearance of the "stratux" wi-fi on all my devices). Subsequent boots were as quick as I was used to (just a few seconds).