Having the same issues in Belgium. I’ve tested several different DNS settings (own unbound DNS server, 1.1.1.1, 9.9.9.9) but without success. No IPv6 on my network.
Roon core is running on a Debian VM, Intel i5-10400 (4 cores, 8GB) but I’ve had the same issues when running on my desktop (i7 8700k, 16GB)
Speedtest gives my around 270/19.
Using Qobuz for streaming
Edit: could be related: Slow loading of page content