Acknowledged
%CELLSIG and %CELLSRV don't return the correct values
%CELLSIG always returns -1 and %CELLSRV always returns unknown for LTE networks.
Apparently this is a long standing issue.
The state of Use New Cell API has no effect.
Samsung S9, Android 9, Tasker 5.8.0.rc3, Verizon 4G LTE