2018-11-25: installed amanda 3.5.1-2+b2
https://buildd.debian.org/status/fetch.php?pkg=amanda&arch=amd64&ver=1%3A3.5.1-2%2Bb2&stamp=1541073216&raw=0
2018-11-28: installed glib 2.58.1-2
2019-07-21: last good backup before bugreport (not 27, my mistake)
2019-07-24: installed amanda 3.5.1-2+b3
https://buildd.debian.org/status/fetch.php?pkg=amanda&arch=amd64&ver=1%3A3.5.1-2%2Bb3&stamp=1563909152&raw=0
2019-07-30: opened bugreport
2019-07-31: workaround with locally built amanda 3.5.1-2
2019-08-03: installed glib 2.60.6-1
2019-08-03: installed amanda 3.5.1-2+b3 (again) and it works
If there is a way to ensure "amanda" transitions from unstable into
testing only after its dependencies, that would be great. If this
situation is normal and unavoidable, please feel free to close the bug.