Does Spectrum support Edge Chromium?
Yes, Spectrum currently supports Edge Chromium as of Spectrum 10.4.2.1 and above.
Spectrum, by default, uses BASIC Authentication. This can be disabled within Edge and enforced by administrators.
Behavior will be instant login failure (no pop up) when this is on. Work with admins to turn this off, or utilize SAML2 Authentication within Spectrum with a supported IDP.
Group Policies can be in effect that can cause issues.
Your Spectrum machine and clients should allow IE11 Document Mode and IE5 Document Mode.