Do you mean , use some software like sentry.io / New Relic./ Firebase to get some basicly technically feedback from you real customer ?

We have used "Userbrain" in the past to get feedback on UX and user flows. Very useful and easy to set up!

I usually DM people on reddit that might look interested. If I am targeting a very narrow market, then I might use betatesting.com It's paid but it's good value.

Used usertesting.com many years ago. Their testers were "semi-pro". That is, they seemed to do it as a side hustle, and as such, their opinions didn't seem necessarily representative of our target demographic.