ACS Data Users Group

Is there a place where I can download a file with a list of ACS 5 year tables (2021) at the blockgroup (150) geography ?

See the "Table List" file through this page. It lists all detailed ACS tables, and Column G indicates whether the table excludes block groups.

Alternatively, through the IPUMS NHGIS Data Finder, you could select a dataset filter for 2017_2021_ACS5a: 5-Year Data [2017-2021, Block Groups & Larger Areas], and the resulting selection options would be limited to tables that provide block group data.