Lambda for Getting Sums Based on Dynamic Filters

For this part: (IF(Dept = "", nofltr, INDEX(tbl, , XMATCH("Staff & Agencies Involved", hdrs)) = Dept))

One thing I forgot to mention is that the Dept value would need to be formatted for a partial text match. The context is that the data in the "Staff & Agencies Involved" column contains answers from a multi-selection choice question in MS Forms, which comes out looking something like ["Option1","Option2","Option3"]. My understanding is that FILTER() doesn't support wildcards, but some other online sources suggested something like this might work:

.....*(IF(Dept="",noflter,INDEX(tbl,,XMATCH("Staff & Agencies Involved",hdrs))=(ISNUMBER(SEARCH(Dept,Table1[Staff & Agencies Involved]))*.....

This doesn't appear to work, though. Any ideas? Your solution works great otherwise.