You might find this Japanese research article relevant:
"These results suggest that most of N in coffee grounds is insoluble N. However, Wakasawa et al. (1998a) reported that NO 3 -N content of the soil incorporated with coffee grounds gradually increases after 4 months of the application. "
https://www.jstage.jst.go.jp/a...
Field Evaluation of Coffee Grounds Application for Crop Growth Enhancement, Weed Control, and Soil Improvement, Yamane et al.
The article also discusses the potentially inhibitory effects on growth of some plants in the short term. "These results indicated that coffee grounds are useful to enhance long term crop growth, short duration weed control, and soil improvement in agricultural fields by considering the inhibitory effects on
the plant growth for half year after the application."
As an aside, and maybe not relevant for your purpose, coffee grounds aren't necessarily particularly acidic.
