What's interesting, is that despite the app not being updated since 2018, open source, and containing no ads or tracking the reviews are saying it recently became adware.
Searching for barcode scanner in the app store brings you to a horrible sea of ad supported crap ware, and it seems like that crap ware wants to ensure you don't download something that might be decent.
I scraped the latest 1000 reviews (coincidentally almost exactly 12 months worth).
The "adware" reviews are all very recent with large amounts of votes.
They seem to start on December 18, with 162 1-star reviews in the following 25 days -- more than all the 1-star reviews in the 6 months prior.
I wouldn't be surprised if these reviews are not only automated spam, but are constantly being deleted and reposted to keep them "fresh", and at the top of the "relevant reviews".
Charts: https://imgur.com/a/QUyHcHu
CSV of review data: https://pastebin.com/ZanYgd5Y
Used the simplescraper.io Chrome extension (with a little bit of DevTools fiddling) to export a CSV.
Created a pivot table in Excel and charted the results.
The last update I see available is what I have installed - 4.7.8 from September 2018. Definitely no strange behavior from it.
But I also use this app for QR-codes, since I was never able to find an alternative. The vast permissions required make me nervous every time I install it... Good to know it is on F-Droid as well, built from a source tarball, so should be OK [1]?
[1] https://f-droid.org/en/packages/com.google.zxing.client.andr...
However all the negative comments about ads are from after November 2020. Clearly a smear campaign.