How should euro-zone countries' public debt be considered?

Euro-zone countries' fiscal deficits will be massive in 2020 and certainly still in 2021. This has launched a debate on the difficulty there could be in repaying the public debt: will tax increases and public spending cuts be necessary? In reality, there is no problem related to the repayment of public debt: The first possibility is that the ECB buys and continues to buy the issued public debt (government issuance, debt mutualised by Europe) and refrains from reducing the size of its balance sheet in the future. We then know that government bonds irreversibly held by the central bank are de facto cancelled, and will therefore never have to be repaid; The second possibility is that if the ECB has to reduce its public debt purchases, for example because of a surge in inflation caused by the rise in production costs due to the new health standards, there will be large issu ance of mutualised European debt to replace government issuance. Interest rates on this mutualised European debt would be very low, and this debt could have a very long maturity. The servicing of this debt would therefore be very low; The third possibility is that if the ECB stops monetising fiscal deficits and mutualised European debt is not possible, as a few countries are reject ing this solution, each euro-zone country will issue national public debt with a very long maturity. Given the current interest rate levels, the return on investments financed with this debt would be significantly higher than the interest rates for the vast majority of euro-zone countries, so these countries would have no problems repaying the debt. In this third case, there remains the risk that in some peripheral countries (Italy, Greece?) the very long-term interest rate will be higher than the return on investments financed by the debt, and therefore that these countries will have to switch to a more restrictive fiscal policy in the future in order to remain solvent.