Thank you both. Good to know that it was solved later, but also good, that I can solve the problem even with Rationalize[] and then N afterwards.
Det[Rationalize[m]] // N
-1.70567*10^12
In[11]:= m2 = Rationalize[m]; Det[m2] Out[12]= -(873303244870245693606726965155785607800007/\ 512000000000000000000000000000)
Hi Martin,
Looks like the problem was fixed in a later version.
$Version (* 12.2.0 for Mac OS X x86 (64-bit) (December 12, 2020) *) Det[m] (* -1.70567*10^12 *)
