Information sources vary per country, but there should be lists like this one [0] for Germany. Access condition are a bit of a mess. EuroHPC was started to harmonize things a bit [1] but also here the reality is complicated at least for the 50% funded by national money.
[0] https://gauss-allianz.de/en/hpc-ecosystem
[1] https://access.eurohpc-ju.europa.eu/