Slovakia, 300GB for 13 EUR/month, no texts and calls included. Those are 5 cents I think.
The carrier has an agreement with another one for coverage extension, but with official FUP of 20GB in that network.
This carrier however disregards that and instead allows up to 80GB, but for a few months after enabling 4G from that other carrier the FUP wasn’t applied at all.

But it’s not all sunshine and rainbows.

It operates on that other network like MVNO, and if your phone decides to stick there, which people report happens a lot, say hello to far lower FUP instead. The carrier’s own network is also generally far slower.
I also found a little network issue (tested with 2 phones) where receiving calls are broken in a fairly specific scenario, but I don’t know how to report that. To keep it short, if VoLTE isn’t available, when switching from 2 of the 4G bands to one of the 2G bands, the call fails to connect after several long seconds of silence on caller end, and no notification of failed call attempt is sent.

I can work around both issues by selecting specific bands as needed manually, but that generally requires root and use of app like Network Signal Guru (inconvenient).
This allows me to decide whether I want more data amount, faster network speed, better outgoing call coverage, or higher chance of receiving a call. Yeah… their network sucks.

I also believe they break the EU roam like at home regulation:

Most plans only have half the data amount it seems they should have, but maybe I just calculated that wrong.
But this plan I have has… ZERO data for EU roaming.

2 x (price of mobile bundle excluding VAT / regulated maximum wholesale cap per GB) = data limit (in GB) when roaming

Hmmm… how does that give a zero.