Or 3 month Euribor is now -0.281%, so with say 1.2% margin for bank the current interest would be 0.92%. Obviously with no guarantee for it staying that low.

http://www.euribor-rates.eu

You can't compare 3 month term interbank loans to a 30 year term mortgage. 30 year tbills are around 2.25%.

That wasn't a comparison to the 30 year fixed mortgage, just brought up an alternative.

And this is not theoretical, the usual way to get a mortgage around here is Euribor with a margin for the bank added, practically no-one gets decades-long fixed mortgages.

A 3mo interbank rate is not an alternative to a 30 yr consumer mortgage.

Not sure what you mean -- as I said, that's what people do around here: interbank rate + bank marginal. Fixed 30-year mortgages are very rare.

2.875 on a 15 year here