Google slow in indexing its Google groups link slowly

I am running link indexing speed test.

I created a google group and update it with relevant materials once per week.

Over a month has passed and the group link was not indexed.

Of course, it has no sitemap, lo extra links to it - all this would solve the problem for few days (latest experience due to good link partners was 2 days for indexing).

But in any case, I thought google could be more friendly and faster in indexing its link on informational feed sources.