Am i correct that tables B05001/C05001 on citizenship are not available at the block group level?
I have been unable to winkle out any useful citizenship table for groups, to calculate pct citizen.
Correct. See Appendix A at www2.census.gov/.../ACS_2019_SF_5YR_Appendices.xlsx
However, you could look at tables B29001, B29002, B29003, and B29004, if all you need are numbers of citizens of voting age
There are a selection of variables, considered sensitive, that Census Bureau does not publish at the BG level. Citizenship is one of these. (but is available though for tracts, places, counties, etc.) See censusreporter.org/.../
Having said that... if you can wait til spring, the Outgoing Administration commanded Census Bureau to produce a CVAP tabulation of 2020 Census for all geog levels. It is now in the works, unless someone stops it.